The meaning of nonce in which I'm interested today is the one found in the phrases for the nonce, or nonce word.
This lovely bouncy word is an example of false splitting. That means it's one of those words like nickname or apron where an n has migrated from one word to another: for example, an apron used to be a napron, and a nickname used to be an ekename.
Nonce is basically the same word as once, and a nonce word is a word coined for a single occasion. These are often deliberately nonsensical words like wud or shulp, designed to be used to research the way people learn language (a question like what's the most likely word for more than one wud? might be asked, for example).
For the nonce is a similar sort of thing and means for the present occasion.
Word To Use Today: nonce. This word appeared in the 1100s from the phrase for then anes, literally for the once. (The n at the end of then in this phrase, which, as already indicated, means the, is a dative singular. A dative singular is, basically, a bit added onto a word to make it plain exactly what part it plays in the phrase. English used to use them all the time, but it's now sensibly jettisoned very nearly all of them.)