cabbageyoudaoicibaDictYouDict[cabbage 词源字典]
cabbage: [14] The shape of a cabbage, reminiscent of someone’s head, led to its being named in Old French caboce, which meant literally ‘head’. English acquired the word via the Old Northern French variant caboche (whose modern French descendant caboche, in the sense ‘head’, is said to provide the basis for Boche, the contemptuous term for ‘Germans’).

It is not known where it comes from ultimately; etymologists used to link it with Latin caput ‘head’, but that theory is no longer generally accepted. The Old English word for ‘cabbage’ was cāwel, which remains with us in the form of various Germanic relatives such as kohl-rabi, cauliflower, and Scottish kale.
[cabbage etymology, cabbage origin, 英语词源]
cabbage (n.)youdaoicibaDictYouDict
mid-15c., caboge, from Middle French caboche "head" (in dialect, "cabbage"), from Old French caboce "head," a diminutive from Latin caput "head" (see capitulum). Introduced to Canada 1541 by Jacques Cartier on his third voyage. First written record of it in U.S. is 1660s.

The decline of "ch" to "j" in the unaccented final syllable parallels the common pronunciation of spinach, sandwich, Greenwich, etc. The comparison of a head of cabbage to the head of a person (usually disparaging to the latter) is at least as old as Old French cabus "(head of) cabbage; nitwit, blockhead," from Italian cappuccio, diminutive of capo.