butch, v.² — Green’s Dictionary of Slang

butch v.²

butch up (v.)

(gay) to emphasise one’s masculinity/mannishness.

1993

R. Rodi Closet Case 92: And if it butches him up a little, well, is that so bad? [Simes:DLSS].

butch it up (v.)

(US gay) to act in a ‘masculine’/macho manner, esp. of one who is not (yet) ‘out’.

1963		‘Cory’ & Leroy Homosexual & Society 262: butch it up, v. To make an effort or a pretense to be butch. Particularly used for a male homosexual who is attempting to hide his homosexuality from heterosexual acquaintances [Simes:DLSS].
1968		M. Crowley Boys in the Band 25: I butched it up quite a bit. And [...] I really thought I was straight [Simes:DLSS].
1972		B. Rodgers Queen’s Vernacular 39: ‘Butch it up, Mac, Tilly’s got us spotted’.