Green’s Dictionary of Slang

1. (US prison) a new prison inmate.

1971

(con. 1930s) J. Brown Monkey Off My Back (1972) 39: This gentle giant put us through the paces that all ‘skinners’ endure — being shorn of hair, stripped and deloused, then undergoing examination for any communicable diseases.

2. (US prison/Und.) a rapist; a sex offender.

1972		B. Rodgers Queens’ Vernacular 182: skinners 1. hands that can’t stay to themselves. [...] 2. sadists, whipcrackers.
1984		Partridge DSUE (8th edn) 1079/1: since ca. 1950.
1989		A. Vachss Hard Candy (1990) 92: You don’t work with drunks, you don’t work with dpe fiends, you don’t work with skinners.
1992		Bentley & Corbett Prison Sl. 37: Skinner [...] An inmate who is in prison for rape.
2000		Other Side of the Wall: Prisoner’s Dict. July 🌐 Skinner: Sex offender (ME).