Words for milk, and related words, in Celtic languages.

Words marked with a * are reconstructions.
Proto-Celtic |
*laxto- = milk |
Old Irish (Goídelc) |
lacht [l͈axt] = milk |
Irish (Gaeilge) |
lacht [l̪ˠɑxt̪ˠ / l̪ˠaxt̪ˠ] = milk, yield of milk; tears
lachtadh = lacation; flooding (of eyes)
lachaí = nursling
lachtach = lactic, milky; tearful
lachtbhán = milkwhite
lachtmhar = lactiferous, milky, abounding in milk |
Scottish Gaelic (Gàidhlig) |
lac, lachd = sweet milk |
Manx (Gaelg) |
laghtveih = milk gauge, milk tester |
Proto-Brythonic |
*llaɨθ = milk |
Middle Welsh (Kymraec) |
llaeth = milk |
Welsh (Cymraeg) |
llaeth [ɬaːɨ̯θ / ɬai̯θ] = milk; milk-like substance, latex; milt, soft roe
llaetha(f), llaethu = to yield milk, lactate, feed with milk, turn to milk
llaetheiddrwydd = milkiness, lactescence
llaethiad = lactation
llaethlyd = milk-like, milky
llaethog = milky, abounding in milk
llaethogrwydd, llaethedd = milkiness
llaethwraig = milkmaid, dairymaid, good milker
llaethyddol = dairy, dairying
y Llwybr Llaethog the Milky Way |
Old Cornish |
lait = milk |
Middle Cornish |
leth, leyth = milk |
Cornish (Kernewek) |
leth = milk |
Breton (Brezhoneg) |
laezh [ˈlɛːs] = milk |
Etmology: from the Vulgar Latin *lacte (milk), from the Latin *lac (milk), from the Proto-Indo-European *ǵlákt [source].
Proto-Celtic |
*mlixtus = milk |
Old Irish (Goídelc) |
mlicht [mʲlʲixt] = milch, in milk (of cattle) |
Middle Irish (Gaoidhealg) |
blicht = milk |
Irish (Gaeilge) |
bleacht [bʲlʲaxt̪ˠ] = milk, milk yield |
Scottish Gaelic (Gàidhlig) |
bliochd [blixg] = milkiness, milk
bliochdmhor [blixg(v)ər] = milky, full of milk
bliochdach = milky, like milk, lacteous |
Manx (Gaelg) |
bluight = lactiferous, lacteal, galactic
bluightagh, ollagh vluight = milking cows |
Proto-Brythonic |
*bliθ = milk |
Middle Welsh (Kymraec) |
blyth = milk
lleurith = milk |
Welsh (Cymraeg) |
blith [bliːθ] = milch, lactating (of cow, etc), full of milk, in calf, in lamb, pregant, fruitful, productive, nourising; milk, dairy produce, lactation, dairying; profit, gain, advantage
blithog, blithiog = milch, giving milk, full of milk, fruitful, productive, bearing offspring
llefrith [ˈɬɛvrɪθ] = milk, new milk, sweet milk, fresh milk |
Old Cornish |
leuerid = milk |
Breton (Brezhoneg) |
livrizh = milk |
Etmology: from the Proto-Indo-European *h₂ml̥ǵtus, from *h₂melǵ- (milk, to milk) [source].
The Welsh word llefrith, which is used in North Wales, comes from llef (weak) and blith (milk) [source].
Proto-Celtic |
*bandyo- = drop |
Old Irish (Goídelc) |
banne = drop, pustule
bannán = small drop, droplet |
Middle Irish (Gaoidhealg) |
bannae, bainne, banne = drop, pustule, milk |
Irish (Gaeilge) |
bainne [ˈbˠaɲə / ˈbˠan̠ʲə] = milk
bainniúil = milky, milk-yielding
bainniúilacht = milkiness |
Scottish Gaelic (Gàidhlig) |
bainne = milk
boinne [bɔn̪ʲə] = drop, small quantity, liquid measure
boinneag [bɔn̪ʲag] = droplet, little/small drop, (alcoholic) drink
boinnean [bɔn̪ʲan] = droplet, wee drop |
Manx (Gaelg) |
bainney [banʲə] = milk |
Middle Welsh (Kymraec) |
ban = drop (?) |
Middle Cornish (Cernewec) |
ban, banna, banné = drop, a jot, the smallest portion of anything |
Cornish (Kernewek) |
banna = bit, drop |
Middle Breton (Brezonec) |
banne, bannhe, bannech = drop, droplet |
Breton (Brezhoneg) |
banne [ˈbã.nːe] = drop, droplet, glass
banneata = to drink shots |
Etymology: uncertain. Possibly related to French bain (bath) in French, baño (bath, bathroom, toilet), bagno (bath, to swin, bathe, bathroom) in Italian, and bania (jug, can, container, churn) in Polish [source].
Other words for milk in Proto-Celtic include: *glaxtā-, *melgos-, *mlig-e/o-, *seigi- and *sutu-.

Sources: Wiktionary, Etymological Dictionary Of Proto Celtic, In Dúil Bélrai English – Old Irish glossary, eDIL – Electronic Dictionary of the Irish Language, Teanglann.ie, Am Faclair Beag, An etymological dictionary of the Gaelic language, Fockleyreen: Manx – English Dictionary, Online Manx Dictionary, Gaelg Corpus, Geiriadur Prifysgol Cymru, Lexicon cornu-britannicum : a dictionary of the ancient Celtic language of Cornwall, Gerlyver Kernewek, Devri : Le dictionaire diachronique du breton, Dictionnaires bilingues de Francis Favereau / Edition Skol Vreizh, TermOfis