Nonce is an intriguing word with a range of meanings, I just stuck to the relevant definition.

Wait what? Nonce is a term for sex offender?? Maybe you mean to say it’s a slang that can mean pedo?

It can mean any sex offender, rapists, flashers, etc.

I’ve heard Brits call dummies nonces too.

Took me a bit to figure that one out - dummies as in idiots, not as in soothers you give to babies.

For me, I think of cryptographic nonces when I hear the word lol

That's a much more recent use, apparently "number used once" but I suspect it falls under "they knew".