Green’s Dictionary of Slang

(US black) ‘the act of doing a shadow dance’ (Durst, The Jives of Dr Hepcat, 1953).

1936		Andy Kirk ‘I’se A Muggin’’ 🎵 I’se a-muggin’, boom doddy doddy, / I’se a-muggin’, / Dick’s a-muggin’! / Well, mug on out there, cat!
1953		L. Durst Jives of Dr. Hepcat (1989) 6: Kitties pick up on this riff by C. It’s a gas, righteous beats and upstate muggin makes this cool Jim all the way uptown, let’s dig.