"stupid person," 1909, American English slang, perhaps a shortening of booby. For the "woman's breast" sense, see boobs. Mencken seems to have coined booboisie (1922).
Entries linking to boob
booby n.
"stupid person," 1590s, from Spanish bobo "stupid person," also used of various ungainly seabirds, probably from Latin balbus "stammering," from an imitative root (see barbarian).
The specific sense "dunce in a school class" is by 1825. Hence also booby prize "object of little value given to the loser of a game," attested by 1884:
At the end of every session the dominie had the satirical custom of presenting his tawse [a corporal punishment implement used for educational discipline] as a "booby-prize" to some idle or stupid lout whom he picked out as meriting this distinction so that next time they met he might start fresh and fair with new pair for a new set of classes. [Ascott R. Hope, "Dumps," Young England magazine, September 1884]
Booby trap is by 1850, originally a schoolboy prank; the more lethal sense developed during World War I. Booby-hatch "wooden framework used to cover the after-hatch on merchant vessels" is from 1840; as "insane asylum" by 1936.
boobs n.
"breasts," 1929, U.S. slang, probably from much older term boobies (late 17c.), related to 17c. bubby; all perhaps ultimately from Latin pupa, literally "little girl," hence, in child-talk, "breast." Or else it is a natural formation in English (compare French poupe "teat," German dialectal Bubbi, etc.).