Prosthetic f, backformation or eagal and feagal

Prosthetic sounds are nothing unusual in the… ah OK, right you are. A prosthetic sound is a "random" sound that gets stuck in front, the middle or at the end of a word to make it conform better with the sound rules of whichever language.

Many languages do this, such as Spanish. Spanish phonology (sound laws) has a rule saying that no word may begin with [sp] [st] or [sk]. However, there are words in Spanish which either have these initials historically or have them from loan words coming into Spanish. To get around this problem, Spanish phonology says "prefix [e]" … so Latin spīritus, scola, stabilis become espirito, escuela, and estable. Similarly Scandinavia, spot and Stockholm become Escandinavia, espot, and Estocolmo.

Errr and backformation?

Backformation means that speakers of a language take a native or adopted word and re-analyse it, as it were. This often happens in loanwords or native words whose meaning has become opaque. Opaque, when a linguist uses the word, means that the meaning is not clear from just looking at the word. For example, you can look at the word drumstick and figure that it's a stick that's used with a drum. But no matter how hard you stare at a hot toddy, chances are you won't figure it comes from a Hindi word for a palm-tree.

Where was I? Ah, backformation. English, for example, adopted the French word for cherries, cerise from Latin ceresia, both mass nouns which means there is no singular form. But because English has a very prominent -s plural, English speakers figured that the s must obviously be a plural. So, if many of those little fruits are cherries, one must obviously be - a cherry. This is called backformation. Gaelic does that too, but because it has the phenomenon of lenition at the beginning of words, unlike English, it tends to create backformations at the beginning of words.

Now, Gaelic phonology does not forbid words beginning with a vowel (don't laugh, some languages have no words beginning with vowels!) but it does have something like prosthetic sounds. Most notably [f]. In the case of Gaelic this comes about when native speakers re-interpret words beginning with a vowel as "a word which has lenited X". However, there is more than just one backformation. Let's have a quick look at what can happen:

[h] ⇨ [t], [d] or [s]	because lenited [t] or [s] yields [h], failing that, you drop it. [d] is rare, possibly via [t].
[ð] ⇨ [d]	because lenited [d] used to yield [ð]
[θ] ⇨ [t]	because lenited [t] used to yield [θ]
[v] ⇨ [u] or [b]	because lenited [b] yields [y] or failing that, sounds a bit like [u]
[j] ⇨ [g]	because lenited [g] yields [ʝ]. This happens in words with a soft onset which is an almost [j] sound, as in English iota, which to Gaelic ears sounds like the word begins with gh th or dh
initial vowel ⇨ [f]	because lenited [f] is silent - and this is by far the most common one, and about the only one, still active in modern Gaelic
initial vowel ⇨ [t], [s] or [ʃ]	Because the masculine article in front of a vowel is an t- and the t- is sometimes wrongly attached to the noun itself. In rare cases, via t » t-s » this might become [s] or [ʃ]

There are more, but those are the most common ones.

Examples

Examples to your heart's content, a lot of them are loanwords, except the ones beginning with f + vowel:

Source	Meaning	Gaelic	Irish
Latin fundus	foundation	bonn	bonn
Latin jocosus	droll	geòrcaire glutton
Latin iota	a bit	tiota*	giota
Latin vulpes	fox (possibly whelp/hvelpr)	uilp*
Norse háfr	hand-net)	tàbh	tábh
Norse hálsa	slacken	allsadh/abhsadh
Norse hamarr + ey	steep rock + island	Hamarsaigh
Norse hár + bolstaðr	high + farm	Tàbost
Norse hjálm	helm	failm
Norse hjalt + land	hilt + land	Sealtainn	Sealtainn
Norse hlíð	gap (in a fence)	(cachai)leith
Norse hnúkr	knoll	cnuachd
Norse hǫll	hall	talla	halla
Norse hǫmull	swingle-tree	amall
Norse húfr	hull		ub (prow)
Norse hrúga	peat-stack	ruc
Norse þeisti	black guillemot	taibhse
Norse þili (or poss. OE deal	wainscot	déile	tile
Norse þopta	thwart	tobhta	tochta
Norse Þorketill	(name)	Torcall
Norse Þórmóðr	(name)	Tormod
Norse Þorskr	cod	trosg	trosc
Norse Þurs	giant, ogre	tursa (tursaichean/tursachan)
Norse ulfr	wolf	uilbh/ulbh
Norse ulfr	wolf	ulfhart (possibly)
Norse vindáss	windlass	unndais	undás
Norse vindauga	window	uinneag	fuinneóg
Old Irish áinne	ring	fàinne	fáinne
Old Irish allas	sweat	fallas	allas
Old Irish ásaim	I grow	fàs	fás
Old Irish ecla	fear	(f)eagal	(f)eagla
Old Irish ilur	eagle	(f)iolaire	iolar
Old Irish osclaicim	I open	fosgail	oscail
Old Irish rádharc	vision, view	fradharc	radharc
Old Irish uacht	cold	fuachd	fuacht
Old Irish uath	hate	fuath	fuath
Old Irish urusa	easy	furasta	furasta
French jeune	young	diùn-laoch young hero
Scots webster	weaver	buabastair
Scots/English hackle	(possibly)	sisteal	siostal
Scots/English haggis		taigeis	hagaois
Scots/English Harlaw	hard + law	Arla
Scots/English harness		àirneis
Scots/English hasp		deasp
Scots/English hatch (n.)		saidse	haiste
Scots/English halberd		taileabart	halbard
Scots/English heckle (n.)		seiceal	seiceal
Scots/English hoe		tobha	n/a
Scots/English hogshead		tocasaid	oigiséid
Scots/English thaft		tobhta	tochta
Scots/English throng		trang "busy"	trang(láil)
Scots/English viscount		biceas	bíocúnta
Scots/English vervain		bearbhain	beirbhéine
Scots/English vice	(tool)	bidhis	bís
Scots/English walewort		mulabhar/mulart
Scots/English waistcoat		siosacot/siostacot	bástchóta
Scots/English wheel		cuidheall
Scots/English whisk		fusgan
Scots/English witch		buidseach	buitseach
Scots/English woodcock		budagoc
Scots/English woodcock		fudagag
Scots/English woodcock		udacag
Scots/English wormwood		burmaid/mormanta	mormónta
Scots/English worsted		bursaid	mustairt
English Yankee		Geangach
Scots/English yeast		giost/giosg	giosta
Scots/English y(e)oman		gìomanach	gíománach

*although tiota in Gaelic is conceivable a case of the t of the definite article latching onto the noun i.e. an t-iota > an tiota. But with Irish giota clearly a backformation, it could equally be iota > *thiota > tiota.

On occasion, even the permissible fricative f- turned into p- through the same process:

Source	Meaning	Gaelic	Irish
Norse floti	fleet	plod	plod
Scots/English flour		plùr	plúr
Scots/English flower		plùirean	plúr/plúirín
Norse hjálm	helm	palmair (via failm)	pailmaire/failmaire

Even without turning to loanwords, this can get downright crazy when you throw the effects of nasalization and rebracketing into the equation. The Old Irish root of the word nettle is nenaid which eventually yields neannt + ag. But this is where the fun starts. Because this is very common with the definite article, an neanntag quickly results in people thinking of this as an eanntag. Which some folk of course mis-interpret as a case of an fheanntag, giving rise to feanntag. Not to be outdone, some folks took an neanntag and considered it to be the result of nasalization i.e. they assumed the word had to be an deanntag. The only one missing for a full set is *teanntag!

English may excel at punning but there's nothing quite like the interplay between lenition, nasalization and rebracketing in Goidelic languages to delight the phonologist and to drive etymologists to substance abuse...

Or cheat

Cheating works too of course, just as an aside. This happens particularly with loanwords which have an initial h. Initial h does make a regular appearance in Gaelic - but only in certain grammatical contexts, such as the genitive of feminine nouns or the plural if there's a definite article, for example doras na h-eaglaise or na h-ùbhlan. So in some cases, when Gaelic borrowed words which began with h, it slaps an extra article on which wasn't there in the language it borrowed from. For example:

Source	Meaning	Gaelic
Norse hǫfn	harbour	Na Hann
Norse haugr	mound	Na Hogha Bheag
Norse hérað	type of administrative unit	Na Hearadh
Scots Foxhole		A' Bhogsolla

Often, like in Na Hogha Bheag, you're left with a word which obeys the sound rules of Gaelic but has what looks like shifty grammar (you'd expect *Na Hogha Beaga) which is often a telltale sign of a fricative-initial loanword that was squeezed into a corset to make it sound ok.

But why are there so many place-names with initial h?

Good question. I'm making an educated guess here but I think it's because place names, in the past, mostly occurred in the genitive or dative. Today we put up roadsigns and have lists of place names but that's a fairly recent thing. When you're actually talking 'normally', usually place names don't appear in grammatical isolation like that. And in Gaelic, that puts the place name into a leniting environment. Let's use Glaschu as an example. You can be 'in' Glasgow, which is probably the only non-leniting example: ann an Glaschu. But if you're going to Glasgow, you're a' dol a Ghlaschu and the people or shops of Glasgow are muinntir Ghlaschu and bùithtean Ghlaschu.

So ignoring the modern past-time of writing, even a native Gaelic place name like Tairbeart would very often have a (spoken) initial /h/: a' dol a Thairbeart, muinntir Thairbeart and so on.

So in context, place names like the examples below don't jar as much in the ears of a native as some others might.

Source	Meaning	Gaelic	Anglicised as
Norse hár + klettr	high + cliff	Hàcleit	Habost
Norse heastr + staðr	horse + farm	Heasta	Heaste
Norse horna + fjall	horn + mountain	Hòrnabhal	Horneval
Scots haugh + kirk		Hacraig	Halkirk

Simplifly, simplify

No, languages don't always simplify stuff because otherwise we'd all be going round pointing at stuff saying 'uh' and nothing else. But let's leave that topic for another article. Another thing that effectively hides the origins of many Gaelic words is the simplification of certain sounds, either because this change happened throughout the language anyway or because it was necessary to adjust the sounds to fit the language (like the th > t change above).

For example, a language internal process changed many nd/nt sounds to nn and lt/ld to ll. You're probably aware of the coltas/collas issue. That's just an instance of a language internal simplification of lt to ll, nothing to do with English.

So here are some fun examples:

Source	Meaning	Gaelic	Irish
Latin argentum	silver	airgead "money"	airgead
Latin candela	candel	coinneal	coinneal
Latin hic pāx datur	peace*	pòg "kiss"	póg
Norse eyland	island	eilean	oileán
Old Irish cruind		cruinn	cruinn
Scots/English doctor		dotair	dochtúir

• part of the old Celtic liturgy where peace was given just before Communion, involving a symbolic kiss

Let's talk about your sister

A particularly bizarre example of this is the Gaelic word for sister because it went through this several times:

1. Indo-European used swesōr.
2. Proto-Celtic used swesūr - Proto-Celtic, as in before Brythonic (Welsh 'n all that) and Goidelic (Gaelic 'n all that) split.
3. Old Irish used siur AND fiur. OK, this requires some explaining. In the days before Old Irish, the words for my, your and his already caused lenition. So far so good, but this meant that Proto-Celtic swesūr became hwesūr, just like leniting s today. But as the hw never sat well with the language (a bit like thing becoming fing in London) it soon turned into an f, but our, your (pl.), their didn't, and didn't lenite. So, by the time we arrived at Old Irish, unlenited our/your/their sister had become ar siur, far siur, a siur, but lenited my/your/his sister had become mo fiur, do fiur, a fiur. Yes, slightly confusing.
4. To get from Early Irish fiur/siur to the modern forms, we now have to go via the genitive forms for Gaelic (something which did not happen in Irish - don't sigh). So modern Irish just continues with the old roots using deirfiúr "sister" from deirbh fiur "true sister" and fiúr "kinswoman" (because two words are better than one…).
5. However, Scottish Gaelic grabs the old genitives, fethar/sethar, and muscles them into piuthar. The p appears, of course, because f is quite obviously lenited p. Now why didn't you think of that before? ☺

Anyway, to get back to the point, this is the reason why you will hear some Gaelic speakers pronounce certain words with f and some without. It's a process that's still in the middle of happening, so until the language decides on whether it will stick with eagal or adopt feagal, you can take your pick about which one you prefer. It makes no difference, either way, as both are good Gaelic words.