cicisbeo
A man who escorts a married woman to social functions, especially in 18th-century Italy; a married woman's lover.
historical
My old Cicisbee says it would do: & he is (or was poor fellow!) a famous Scholar.
Where it comes from
Borrowed from Italian cicisbeo, of onomatopoeic origin.
Adapted from the Wiktionary entry cicisbeo (CC BY-SA 4.0).