The story
From "Who's on First?", a comic routine from 1930s vaudeville made famous by Abbott and Costello, in which two people discussing a baseball team become confused by names such as "Who" and "What".
Etymology from Wiktionary, CC BY-SA 4.0.
who's on first
Today it means: A situation in which confusion arises due to homophones and similar misunderstandings. Full definition →