The story
Paraphrase of a line in Alphonse and Gaston, an American comic strip by Frederick Burr Opper.
Etymology from Wiktionary, CC BY-SA 4.0.
after you, Alphonse
Today it means: An exchange indicating excessive formality or effort at politeness, particularly where two people each refuse to go forward because each insists on allowing the other to go forward first. Full definition →