Where does “gaeilge” come from?
gaeilge (Irish) comes from Irish Gaedhilge, from Irish Gaedhealg, from Old Irish Goídelc, from Old Irish Goídel, from Old Welsh Guoidel, from Proto-Brythonic guɨðel, from Proto-Celtic wēdus, from Proto-Indo-European widʰu- — forest, wood; tree, beam.
Ancestry of “gaeilge”, step by step