Where did this saying originate? (see details)

Hmm, I thought I had that answer right around here someplace.

pssst – it should be “lose.”

Perhaps somewhere around the time of the French Revolution?

I’ve also heard “if it wasn’t glued on” and “if it wasn’t screwed on.”

^^In my linguistically correct family, it was always “If it weren’t screwed on…” with the explanation that “your head is, indeed, attached.” That’s the subjunctive, dude.

It is part of the American English idiom. Idioms evolve from person to person without much documentation.