[rocqua]

Is the term that old? I was told it literally meant N(umber)once.

[dtf]

Yes, the construction "for the nonce" goes back to the Middle Ages. The concept of a "nonce word" goes back to 1884, according to this article.

https://www.dailywritingtips.com/nonce-words-for-the-nonce-a...

[OJFord]

I'm not necessarily arguing there's shared etymology, but consider 'for the nonce' - it's not merely a made up word used exclusively in cryptography.