10th cent. From Latin caput "head." In Vulgar Latin caput may have meant the end as well as the beginning, as seen in Italian far capo "to commence."
From Proto-Italic *kaput 'id.' From an unknown pre-Indo-European substrate language *kap- "cup."
Romance: Western Vulgar Latin: Asturian cabu, Portuguese cabo, Galician cabo, Catalan cap, French chef, Italian capo; Eastern Vulgar Latin: Aromanian cap, Romanian cap
Celtic: Goidelic *kapuku-: Old Irish cúäch "cup;" Brythonic *kapuku-: Middle Welsh cawg 'id.'
Germanic: East Germanic *haubeda-: Gothic haubiþ; North Germanic *habuda-: Old Norse hǫfuþ; West Germanic *haubeda-: Old High German haubit, Old Frisian hāved, Old English hāved (English head); West Germanic *habed-: Old English hafudRe: Beekes (1996), the word seems borrowed from another language. Cognates in other languages point to *a in Proto-Indo-European - a vowel which did not exist. If one reconstructs *kh2p- we must account for a missing full-grade **keh2p-. An incongruous a/au variation (Old English hafut versus Gothic haubiþ) cannot be satisfactorily explained by contamination and there is no reason to assume an ablaut that ended in a stop. The suffix -ut in Latin caput is utterly alien to Italic tongues except as the perfect participle, which makes little sense. Admittedly it could be a borrowing from Celtic, but that does nothing to explain the suffix *-it in Germanic, as evidenced in Gothic haubiþ. The most parsimonious explanation is that suffixes *-ut and *-it are remnants from a non-Indo-European language. As a final point, k-initial plain velars words are rare in Proto-Indo-European. Their presence should raise suspicion. On the other hand, Kroonen (2014) believes the words are of native Indo-European stock; he assumed variation in *a/au was due to supplanting the old proterodynamic paradigm with -au- (taken from the oblique form). "Given this situation [above] - which has always been clear - it seems certain the word is a loan. I find it surprising that I nowhere have seen even the suggestion that the word could be non-IE." ~ R. Beekes, "Ancient European Loanwords" (1996)