Words for heads, brains and minds in Celtic languages.

Proto-Celtic	*kʷennom = head *en-kʷennio- = brain
Gaulish	pennon / πεννοου = head
Primitive Irish	ᚉᚒᚅᚐ-ᚉᚓᚅᚅᚔ (cuna-cenni) = head
Old Irish (Goídelc)	cenn [kʲen͈] = head, end inchinn [kʲen͈] = brain
Irish (Gaeilge)	ceann [caun̪ˠ / cɑːn̪ˠ / can̪ˠ] = head; end, extremity; one; chief, main inchinn [ˈɪɲçən̠ʲ] = brain
Scottish Gaelic (Gàidhlig)	ceann [kʲaun̪ˠ] = head; end, close, finish; lid; roof; subject, topic eachainn [ɛnɛxɪn̪ʲ] = brain, brains
Manx (Gaelg)	kione [caun / coːn / coᵈn] = head, headland, chief, ringleader, bottom, poll, end, extreme, close, finish, top-end, top, point of argument, termination, closing, extremity, point, dyke, tribune
Proto-Brythonic	*penn [ˈpenː] = head
Middle Welsh (Kymraec)	penn = head, chief
Welsh (Cymraeg)	pen [əˈmɛnɨ̞ð / əˈmɛnɪð] = head, obverse (of coin); top, summit, roof, highest point; extremity, end, beginning; headland, promontory, projecting point of rock; pole ymennydd brain, brains, intellectual capacity, mind
Old Cornish	penn = head
Cornish (Kernewek)	penn [pɛn:] = head, end, top ympynnyon brain
Old Breton	penn = head, chief
Breton (Brezhoneg)	pen(n) [pɛ̃n] = head, chief, leader empenn = brain

Etymology: unknown, possibly from the Proto-Indo-European *kap- (to hold, seize). The words for brain all mean “in head”.

Old Irish (Goídelc)	in(n)tinn [ˈin͈ʲtʲin͈ʲ] = head, end
Irish (Gaeilge)	intinn [ˈiːn̠ʲtʲən̠ʲ] = mind, mental state, disposition, attention, spirits, intention, accord
Scottish Gaelic (Gàidhlig)	inntinn [ĩːn̪ʲdʲɪn̪ʲ] = (human) mind; intellect, intelligence; intention, purpose
Manx (Gaelg)	inçhyn = brain, grey matter, intellect, spirit

Etymology: from the Latin intentiō (strain, tension, increase, exertion, charge, purpose, intention).

Words marked with a * are reconstructions.

Sources: Wiktionary, Am Faclair Beag, Online Manx Dictionary, Teanglann.ie, Geiriadur Prifysgol Cymru, Gerlyver Kernewek