As t-samhradh or The mysterious t-

Who hasn't wondered about why the seasons behave very strangely in Gaelic. And I'm not talking about the incessant rain.

The words for the seasons are straightforward enough, but when it comes to saying “in the X” they seem to violate everything you have learned about prepositions:

anns an ogha as t-Earrach anns an t-saor as t-Samhradh anns an fhlaith as t-Foghar anns a' ghleann sa Gheamhradh

Summer and Winter are what you would expect them to be, but what about Summer and Autumn? What we have here are actually two frozen forms - two expressions which at one point became so established in the language that they never changed, even when the rest of the language had "moved on". It's like the Queen signing bills with la Reine le veult [la rɛinə lə veylt] in Norman French (in modern French this would be La Reine le veut [la ʁɛn lə vø]) - no one in Britain speaks Norman French anymore, but the phrase has survived the changes of linguistic fortune.

Just accept from me that in Old Irish the case system worked somewhat differently, not totally different, but there were some things which worked differently. The dative case was one of those things and in those days these expressions with the seasons were quite regularly formed (meanings of examples are as above):

is ind áuu (ogha) [isin taː.u] is ind erruch [isin derːux] is int ṡóer (saor) [isin toeɾ] is int sámrad [isin taːvrað] is int ḟlaith (flaith) [isin tɫ̪aiθ] is int fogmar [isin toɣvaɾ] is in glinn (gleann) [isi ʝlinː] is in gaimred [isin ɣaivɾʲeð]

As you can see, Old Irish regularly had is 'in' and int as the definite article in the dative case which lenited s and f. In all other cases it had in (is in chatt (cat); is in bard (bàrd) etc.).

At some point the system changed (you don't want to know, you really don't) and we were left with the modern system which does what we all do: nothing before a vowel (anns an ogha); insert t- before s (anns an t-saor); lenite f (anns an fhlaith); and lenite elsewhere (unless lenition is blocked) (anns a' ghleann). But because by then the phrases in spring/summer/autumn/winter had become so established, they didn't undergo the same changes.

Modern Irish has fully innovated this system, by the way:

san earrach

sa samhradh

san fhómhar

sa gheimreadh

So, as t-Earrach is 100% correct in modern Gaelic, even though it reflects something that was common a long time ago. Isn't language wonderful? Enjoy your summer!