What does banana oil mean in 1920s slang?

Excuse me, but I'm curious about a phrase from the 1920s. Could you please tell me what "banana oil" meant in the slang of that era? I've heard it mentioned in a few old movies and songs, but I'm not quite sure what it signifies. Was it a term of endearment, an insult, or something else entirely? Your insight would be greatly appreciated.