Over in the Megyn Kelly thread is a sidebar discussion about the origin of the word "bimbo." Several posters pointed out that it is an Italian term for (male) baby, and I want to use this hook to talk about a magnificent resource, The Historical Dictionary of American Slang, edited by J.E. Lightner. Published by Random House beginning in 1994, only the first two volumes actually appeared because of poor sales. This book is to American slang what the OED is to the English language, and it is invaluable.
According to the HDAS, "bimbo" first appeared in the US in print in 1918, in Rossano "Price of Honor": She flop! An' il bimbo he break da boni.
It is clearly referring here to a male, "il."
In 1920, however, in Zeidman "Burlesque": This Dix bimbo is a dangerous woman ... a sassy girl with ... more than a figure--a physique.
I think it's easy to see how the word for baby would move easily into "Hey, baby" territory, regardless of the infant's original sex. But isn't it cool that within a year the word had gained its current meaning?