Valediction: an expression used to say farewell, especially a word or phrase used to end a letter or message.
In modern times, English valedictions have largely been replaced by short sign offs like "Regards" or "All the best."
Historically and in other languages, they are much more interesting.
"I have the honor to be your obedient servant." A dot Ham. (any Hamilton fans?)
"Mit sportlichen Grüßen": With sporting regards from German.
"Beijinho": Literally "a kisslet" from Portuguese.