What does the word kaput have to do with words like cape, chapter and cap? Let’s find out.
Kaput [kəˈpʊt] refers to something that is out of order or not working in English. It was borrowed from German kaputt (destroyed, broken, out of order, tired, exhausted), which comes from the French phrase être capot (not having won any trick in a card game). The origin of this phrase is uncertain, but capot (bonnet, hood) comes from Old French capote (hooded cloak) a diminutive of cape (cape), from Late Latin cappa (cape, cloak), possibly from Latin capitulāre (head tax, poll tax), from caput (head, top, summit, point, end), from Proto-Italic *kaput (head), from Proto-Indo-European *káput- (head), from *kap (head, bowl, cup) [source].
Cape, as in a sleeveless garment or part of a garment, hanging from the neck over the back, arms, and shoulders, comes from French cape (cape), from Old Occitan capa, from Late Latin cappa (cape, cloak), ultimately from PIE *káput- (head) – see above. Cape, as in a promontory or headland, comes from the same roots, via Middle English cape, Old French cap (cape, headland) and Latin caput (head, top, etc) [source].
Chapter (one of the main sections into which the text of a book is divided) comes from Middle English chapitre (chapter, passage, section of a book), from Old French chapitre (chapter), from Latin capitulum (a chapter of a book), a diminutive of caput (head, top, etc) [source].
Cap (a close-fitting hat, either brimless or peaked) comes from Middle English cappe (cap, hat), from Old English cæppe (hat, hood), from Proto-West Germanic *kappā (covering, hood, mantle), from Late Latin cappa (cape, cloak), from Latin caput (head, top, etc) [source].
So they all share a common root, the PIE *káput- (head) and arrived in modern English by various different routes.
Other words from the same root include cadet, capital and captain, chef, chief(tain) and head in English; hoofd (head, chief, boss) in Dutch; huvud (head) in Swedish; capo (head, boss, chief, leader) in Italian; cadeau (present, gift) in French, and capăt (termination, end, extremity) in Romanian [source].