Fucking DHL is double-dipping: They charged me a tariff inspection fee to import my packages, and now they charge a fee* to request tariff refunds of eligible shipments.

*Or I can make an account on some inscrutable government website, write letters to DHL to get paperwork about my shipments, and try to figure it out myself.

The difference is small and pedantic:

“Once” means “A single time”

“Nonce” means “Used a single time”

Nonce carries extra information that something is being used.

Wikipedia claims this term dates to middle English:

Nonce is a word dating back to Middle English for something only used once or temporarily (often with the construction “for the nonce”). It descends from the construction “then anes” (“the one [purpose]”).

Nonce is used extensively in the context of cryptography to mean “used exactly one time”. Usually this refers to a random number that a server shares with a client to establish secure communications.