Unlike Ayto below, Etymonline doesn't mention any Italian etymons for the English "capital" meaning wealth.
Etymologically, capital is something that is at the top or ‘head’; it comes from Latin caput ‘head’. The various current English uses of the word reached us, however, by differing routes. The first to come was the adjective, which originally meant simply ‘of the head’ (Milton in Paradise lost wrote of the Serpent’s ‘capital bruise’, meaning the bruise to its head); this came via Old French capital from Latin capitālis, a derivative of caput. The other senses of the adjective have derived from this: ‘capital punishment’, for instance, comes from the notion of a crime which, figuratively speaking, affects the head, or life. Its use as a noun dates from the 17th century: the immediate source of the financial sense is Italian capitale. The architectural capital ‘top of a column’ (as in ‘Corinthian capitals’) also comes from Latin caput, but in this case the intermediate form was the diminutive capitellum ‘little head’, which reached English in the 14th century via Old French capitel.
Word Origins (2005 2e) by John Ayto. p 92 Right column.
Why "capitale" started to have the finance related meaning it has in Italian?