Man, do I wish I’d had this available when I was studying Old Irish several decades ago: the electronic Dictionary of the Irish Language (eDIL) “is a digital edition of the complete contents of the Royal Irish Academy’s Dictionary of the Irish Language based mainly on Old and Middle Irish materials.” The About page says:
Despite justified criticism, the Dictionary has been an invaluable tool to scholars and students since its publication began, and it is the most comprehensive and ambitious dictionary of the Irish language ever compiled….
The difficulties in using the paper edition are widely recognised. It contains many inconsistencies and inaccuracies… It is the result of the work of generations of scholars and this reveals itself in varying editorial approaches from fascicle to fascicle. These editorial problems are compounded by the huge chronological span covered by the Dictionary (over one thousand years), the variations in spelling in the sources, the complexity of the grammar of the language and its impact on word forms, and the lack of adequate textual editions from which to work. It would have been desirable to arrange forms and senses chronologically, thereby illustrating the historical development of the lexicon, but the problem of dating Irish texts was, and remains, huge, and the editors were no doubt correct in avoiding this hurdle.
This digital edition will ameliorate many of these problems and for the first time users will be able to make complex searches of discrete data types such as translations, citations, grammatical descriptions and sources. It is hoped that the completed work will be of use to a wide range of students and scholars interested in medieval Ireland including linguists, historians, archaeologists, and geographers, as well as those working in Modern Irish. Students and non-specialists will find it a considerable advantage to be able to find the meaning of a word they encounter in a text without having to necessarily know beforehand which headword it will be found under. Editors will be able to search for matches for words which are only partially legible in the manuscript; linguists will be able instantly to compile lists of particular forms of words.
I decided to look up Félire, a word the student frequently runs into because it’s the usual abbreviation for The Félire of Oengus mac Ongobann, a verse calendar of the saints compiled around 800 that is frequently cited, and I remember having wondered what it meant exactly and where it was from. I found:
io,m. (1 féil) a calendar, almanac: feilere (gl. computus annalis) Thes. ii 34.31. Félire (gl. codice, of an almanac) 16.39 (Bcr 32 a 1 →) = felire Thes. ii 35.31. Esp. a calendar of religious festivals, a martyrology: in titles: Feilire na náomh, Feilire i Ghormáin, O’Cl. Pref. (RC iv 354). f.¤ fírchert, Fél. Ep. 156. ní foigbe … f.¤ bas certu 148. ap. (?) rotúrsem … Félire fer nGoídel 144. Félire ro scrútus i céin ┐ acus 109.
If you click on the abbreviated source names, a pop-up box gives the full citation (Thes. is Thesaurus Palaeohibernicus: a collection of Old-Irish glosses, scholia, prose, and verse, ed. Stokes, Whitley, and Strachan, John, published by Cambridge University Press, 1901-03); if you click on the “1 féil” you get:
i, f. (
cf. W. gwyl), ns. fel (in (Ogham) Sg 70 a marg. feil, Thes. ii 33.30. gs. na feile LL 26 a 50 →. np. feli, Thes. ii 34.29. féli, Fél. Ep. 16. 182. (féli as as. (?) armuinter a ḟéli, Fél. Oct. 2. arricfam a ḟéli, Dec. 30. Possibly ap. though féile occurs later as sg.: go f.¤ an bháis, TSh. 4128). gp. na féle, Fel. Prol. 329. Ep. 80. ndu. dí prím-ḟéil, May 31. féil (gs. np. -i) IGT, Decl. § 14.17. Late pl. féilte, O’Hussey T.C. 160.11. Luc. Fid. 115. A festival, feast-day (almost exclusively of religious festivals): f.¤ ir-Rúaim … nóeb nEorapa uile, Fél. Ap. 20. féil sruith, Mon. Tall. §15. ind náob asa feil bís for ind láo §8. i féil máir maicc Cula, Fél. Ap. 5. ria fél Petair, MacCarthy 15.5. ier bfel Brigde TBC 2473 St = iar n-imbulc LL. féiltin Seaain (= féil tSin S.), O’Gr. Cat. 319.30. Abbott-Gwynn Cat. 363. láa feili Poil ┐ Petuir LL 309 b 33 (Cog. 227). f.¤ ghabhála Mhuire i mbroinn Feast of the Conception TSh. 3269. geimh- readh an ghalair ┐ féil an bháis 4116. ó lá ḟéle na marbh All Souls’ day FM ii 1084.15. ag congmháil láoi féile, Ps. xlii 4. pl. feriae … .i. fele, O’Mulc. 60. feili noeb n-uag SR 267. hi felib mártir LU 1856. isna sabbotib saeraib | isna felib fírnóebaib SR 4574. do bhennuccadh gach áoin onóraighfes na laithe ┐ na féilte BNnÉ 275.12. d’faghbhail na féilteagh so[cl]aecloithi the movable feasts O’Gr. Cat. 309.3. budh ainfesach cleirigh | fana feiltiph fire ZCP x 50.14. Rarely of a secular or pagan festival: atbail Moingfinn aidhchi Ṡamna … conid de garar féil Moingfinne frisin Samain icon daescursluagh BB 264 a 6 (SG 332. RC xxiv 178). feli termini feasts of Terminus (gl. terminalibus) Thes. ii 34.29.
Which not only tells me what I wanted to know (it’s from Latin vigilia) but gives me a whole bunch of citations from which I could get a complete picture of how the word is used. It’s not exactly the OED for Irish, but it sure is a treasurehouse, and I thank wood s lot for pointing me in its direction.