careen: [16] Careen comes ultimately from carīna, the Latin word for a ‘nutshell’, which is related to Greek káruon ‘nut’ and Sanskrit kárakas ‘coconut’. The idea of a ‘nut’ as a metaphor for a ‘boat’ is a fairly obvious one (shell is similarly used for a ‘rowing boat’), and the Latin word came to be used for a ‘ship’s keel’, the raised seam of a walnut perhaps suggesting the line of the timber along the ship’s bottom.
It passed via the Genoese dialect carena into French, where a vessel en carène was turned over on its side so that its keel was exposed; hence the verb. The equation of careen with career ‘go wildly’ is 20th-century and of American origin. [careen etymology, careen origin, 英语词源]