Guilty on both counts :o
OK Owl, I’m a Brit who’s led a sheltered life - what exactly does “nonce” mean? I’ve tried Google and dictionaries, both paper and online, and I’m none the wiser. I’ve heard the word plenty, but never quite “got it”. 
I always thought nonce=ponce
We don’t really. But I would have known what that meant.
Disclaimer: I’m a Yank, so I have only that website’s word for it.
Yeah, that website seems a bit crappy, as its sole source is a TV satire from a couple of years ago…don’t worry, I’m googling further…
Nonce really does mean child molestor.
The “vulnerable prisoner wing” in a prison is where prisoners are kept who are thought to be particularly at risk from beatings by fellow inmates - child molestors and police informers. It is colloquially called the “nonce wing”.
From this English slang dictionary:
*…nonce Noun. 1. A sexual deviant, having been convicted of a sex crime against children. 2. An objectionable or contemptible person, by extension of the definition in noun 1. *
The definition goes onto to suggest it also means “head”, as in, “Use your nonce…”. I must admit this is familiar from when I was young. I’ve never thought about it before but the meaning has changed. Nowdays it is always used as slang for “Sex Offender”.
I have just done a straw poll in my office and 5 out of 5 recognise that useage.
Is that a cite? 
Even better - its “Research”
You may now call yourself Dr. Bonjangles.
A nonce is a child-sex offender (it’s short for nonsense).
The work for head that people above are looking for is “bonce”
Another word for ponce could be “jessie”
Nonce does indeed mean child sex offender.
Nonce as in nonsense, a crime with no obvious personal gain, just a short term mindless act.
It was originally used to cover things like beating up the elderly, any sort of sex crime, including back to the days when homosexuality was illegal.
Ponces are of course Southern Jessies who drink nancy beer, unlike northern types who smerk tabs, and do not own overcoats, preferring to winter out in t-shirt and jeans.
I have a mate who smerks tabs - his name is Pearl. It rhymes with Saul.
Wonderful accent.
This is verging towards the British Regional Accent thread.
As opposed to norvern charvas, neds and radgies who twoc cars, smoke soapbar, drink diamond white (aka “charver cava”) and get pregnant at 14.
…and that’s just the blerks!!