The French acronym for NATO is OTAN (Organisation du traité de l’Atlantique nord).

11/08/2019 UPDATES:

Spanish yields the same acronym as French: Organizacion del Tratado Atlantico Norte. (Thanks, Marcial.)

The name of the standards organization ISO is not an acronym: “Because ‘International Organization for Standardization’ would have different acronyms in different languages (IOS in English, OIN in French), our founders decided to give it the short form ISO. ISO is derived from the Greek isos, meaning equal. Whatever the country, whatever the language, the short form of our name is always ISO.” (Thanks, John.)

Similarly, UTC doesn’t stand for anything. It was agreed as a common abbreviation by English speakers (who otherwise would use CUT, “coordinated universal time”) and French speakers (in place of TUC, temps universel coordonné). (Thanks, Scott.)