The earliest confirmed publication is the 1866 Dion Boucicault play Flying Scud in which a character knowingly breezes past a difficult situation saying, "Excuse me Mr. Quail, I ca n't stop; I 've got to see a man about a dog. '' In a listing for a 1939 revival on the NBC Radio program America 's Lost Plays, Time magazine observed that the phrase was the play 's "claim to fame ''.
where did the phrase going to see a man about a horse come from
the 1866 Dion Boucicault play Flying Scud