Wiktionary
muscle boy
n. 1 (context dated English) A goon, thug, muscular henchman. 2 A bodybuilder, especially one who is homosexual.
Usage examples of "muscle boy".
Mickey Cohen was sitting in a wraparound booth, Johnny Stompanato and another muscle boy sandwiching him.
So I played on her fear of losing that prescription, and it all came out: Eddie jilted her for some muscle boy.