J.M. Silk stands for Jack Master Silk.
As a DJ, Steve Hurley was known around 1983-1984 as Steve "Silk" Hurley. Starting his producer career, he thought about changing his name to the Chicago House styled Jackmaster Silk alias. But Farley Keith Williams, at that time Steve's roommate, changed his name from Farley "Funkin" Keith to Farley "Jackmaster" Funk a week before Steve was able to launch a radio promo tape as Jackmaster Silk.