Aaaah, outdated slang... what the hell do you even MEAN?

Boyfriend: So, one of the great questions of the universe... What is a flibberty, and why would you need to hang it?
Me: ......
Boyfriend: You know, 'flibbertygibbet'.
Me: ........
Boyfriend: A gibbet is where you hang people from, so a fliberty gibbet would be where you hang flibberties. I just wanted to know what one was.
Me: ..........
Boyfriend: Why?
Me: *nod*
Boyfriend: I don't know.