bimbo: [20] Bimbo most recently made its mark on the English language in the 1980s, when it was in heavy use among journalists to denigrate buxom young women of limited IQ who sold the secrets of their affairs with the rich and famous to the press. It was by no means a newcomer, though. It first crossed the Atlantic to America, from Italy, in the late 1910s. In Italian it means ‘baby’, and US slang took it up in the colloquial sense of baby, for referring to a usually hapless fellow.
By the 1920s it was being applied equally to young women, especially promiscuous or empty-headed ones (the latter feature probably reinforced by the appearance of dumbo ‘fool’ in the early 1930s). [bimbo etymology, bimbo origin, 英语词源]