- underarm (adj.)
[underarm 词源字典]
- 1816, "underhand" (in reference to a style of throwing), from under + arm (n.1). First attested 1908 in dressmaking sense of "seams on the lower half of the arm-hole;" as a euphemism for armpit, it is attested from 1930s, popularized by advertisers.[underarm etymology, underarm origin, 英语词源]