How did Louis Armstrong get his name?

Louis Armstrong was born Louis Daniel Armstrong.

He was nicknamed Satchmo/Satch, Dipper, and Pops. Satchmo/Satch, short for "satchel-mouth"; Dipper, short for Dippermouth, a reference to the piece Dippermouth Blues and something of a riff on his unusual embouchure; and Pops, which came from his own tendency to forget people's names and simply calling them "pops".