1599, from Sp. bobo "stupid person, slow bird," probably from L. balbus "stammering" (like barbarian, from an imitative root, cf. Czech blblati "to stammer," Skt. balbala-karoti "he stammers"). Booby prize is 1889, an object of little value given to the loser of a game; booby-trap is 1850, originally a schoolboy prank; the more lethal sense developed during World War I.
from this i believe that the slang term for a woman's chest pair is derived from the slow bird concept, whereby women are oft times slowed down by their boobies.