What does ‘egg’ mean?

Now, an egg, as slang for “a person,” goes all the way back … to the 1600s. But by the 1920s, egg took a rotten turn, shall we say.

Egg as insult for an “obnoxious person” was popularized in the 1920s. A particularly bad egg was a double-yolker.

But it’s not all bad for egg because old egg, an affectionate 1920s slang term for one’s partner, was a popular phrase as well!