Cucumbers

There are a whole raft of nicknames both cons and staff use for sex offenders, particularly those who are segregated for their own protection.

This used to be done under Rule 43, now Rule 45. Hence, a man in protection was "on the numbers". Numbers = cucumbers. Simple, innit?

Sex offenders are most commonly called "nonces". The origins of this are lost in time, though there are several plausible sources. Some years ago, in a fit of professionalism, a governor ordered the screws to stop using the term "nonce". And so the screws began to call sex offenders "stills".

I was daft enough to inquire as to why? Obvious, really, once they told me. . .
"Because they are STILL fuckin’ nonces!"