The oldest attestation we have of the word serenade was in a 1656 dictionary of complicated words. At the time, it had pretty similar connotations as today - a romantic open-air musical performance - but it was more specifically used for performances given at night. The word comes from French sérénade and Italian serenata, which meant "calm sky". That comes from sereno, which meant "open air" and was the noun version of an adjective meaning "clear" or "calm" that you might recognize as being related to our word serene. It's also thought that the definition of the Italian word was influenced by another word, sera, which meant "evening". The word first started to refer to pieces of music used in serenades in the 1720s and has been in use as a verb since 1671.
Hello! I'm Adam Aleksic, a senior studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy trivia, politics, vexillology, geography, board games, conlanging, art history, and law.