Sigle.
"Etymology:
Borrowed from (juridical) Late Latin sigla, itself from Latin singula or signum.
Noun
sigle m (plural sigles)
abbreviation
acronym or initialism
Further reading
“sigle” in le Trésor de la langue française informatisé (The Digitized Treasury of the French Language)."
https://en.wiktionary.org/wiki/sigle