anthem

From Middle English anteme, from Old English antefn and Old French antiene, both from Latin antiphōna, from Ancient Greek antíphōna, itself from antí ("over against") plus phōnḗ ("voice, sound").

The facts given don't trace a specific shift in meaning, only the chain of borrowing from Greek through Latin, Old French, and Old English into Middle English.

It's a doublet of antiphon, meaning the two words descend from the same Latin and Greek source but arrived in English by different routes.