Words for to eat in Celtic languages.

Proto-Celtic	*ɸiteti = to eat
Old Irish (Goídelc)	ithid = to eat
Irish (Gaeilge)	ith [ɪ / ɪh / iː] = to eat, feed, graze; bite; corrode, erode; comsume, destroy; abuse, scold, revile; chew
Scottish Gaelic (Gàidhlig)	ith [iç] = to eat; gnaw, chew, devour; corrode; consume
Manx (Gaelg)	ee [iː] = to eat, consume, feed

Etymology: from the Proto-Indo-European *peyt- (food, nutrition) [source].

Sources: Wiktionary, Am Faclair Beag, On-Line Manx Dictionary, Teaglann.ie

Cornish (Kernewek)	debri [dɛbri] = to eat dybri [dɪbri] = to eat
Breton (Brezhoneg)	debriñ [ˈde.bʁɪ̃] = to eat

Note: the Welsh for to eat is bwyta [ˈbʊɨ̯ta / ˈbʊi̯ta], which comes from bwyd (food) [source].

Sources: Wiktionary, Geiriadur Prifysgol Cymru, Gerlyver Kernewek, Dictionnaire Favereau