Green’s Dictionary of Slang

stropper n.

[fig. use of SE strop, to sharpen a razor]

(US) a large, husky man.

[US]R. Lardner Treat ’Em Rough 74: My command is made up of 7 men that I am the boss of them and they contain Sebastian and Red Sampson and Shorty Lahey and a wop named Janinny or something and a big stropper named Hess [...].