nonce

Meanings

1. The one or single occasion; the present reason or purpose.
2. A nonce word.
3. A value constructed so as to be unique to a particular message in a stream, in order to prevent replay attacks.

1. One-off; produced or created for a single occasion or use. Denoting something occurring once.

1. A sex offender, especially one who is guilty of sexual offences against children.
2. A pedophile.
3. A police informer, one who betrays a criminal enterprise
4. A stupid or worthless person.

Etymology

Inherited from Middle English nonse, nones, a rebracketing of Middle English to þen anes, for þen anes (to/for the once (i.e., the one occasion or instance)), from the dative singular neuter of þe. The cryptography sense is commonly said to be a contraction of number used once, although this is probably incorrect.