I've seen that "for the nonce", which doesn't appear very often in the online versions of dictionaries, is just designated as "somewhat formal" in Merriam-Webster and not designated in the Oxford Dictionary at all. But as far as I can see (no native speaker), the word is quite archaic and hardly used in today's media and literature. The examples I've found are often (not always) like
I pursed my lips and set aside my thirst for the nonce.
Her tendency to discover a touch of sadness had for the nonce disappeared.
So would I be right to designate the phrase as "archaic" for example on flashcards?