the.com/boob

means An informal (and in one sense, crude) word with two meanings: a foolish, careless mistake, or — in its other common use — a woman's breast.

from Two separate words collided into one spelling. 'Boob' meaning fool or blunder traces to Spanish 'bobo' (fool, from Latin 'balbus,' stammering), arriving in English slang around the early 1900s as both noun (a dolt) and verb (to bungle). The breast sense is likely baby talk, a cousin of 'booby' and similar nursery sounds echoing infant babble — not, despite the tempting coincidence, from the same 'fool' root at all. The two meanings simply ended up sharing a house.