buxomyoudaoicibaDictYouDict[buxom 词源字典]
buxom: [12] Originally, buxom meant ‘obedient’. It goes back to an unrecorded *būhsum, which meant literally ‘capable of being bent’, and was formed from the verb būgan ‘bend’, from which modern English gets bow. The sequence by which the word’s present-day sense developed seems to have been ‘compliant, obliging’, ‘lively, jolly’, ‘healthily plump and vigorous’, and finally (of a woman) ‘large-breasted’.
=> bow[buxom etymology, buxom origin, 英语词源]
buxom (adj.)youdaoicibaDictYouDict
late 12c., buhsum "humble, obedient," from Proto-Germanic *buh- stem of Old English bugen "to bow" (see bow (v.)) + -som, for a total meaning "capable of being bent." Meaning progressed from "compliant, obliging," through "lively, jolly," "healthily plump, vigorous," to (in women, and perhaps influenced by lusty) "plump, comely" (1580s). In Johnson [1755] the primary meaning still is "obedient, obsequious."

Used often of breasts, and by 1950s it had begun to be used more narrowly for "bosomy" and could be paired with slim (adj.). Dutch buigzaam, German biegsam "flexible, pliable" hew closer to the original sense of the English cognate.