Green’s Dictionary of Slang

(US gay/prison) a male homosexual, esp. the passive/effeminate member of a couple.

1971		E.E. Landy Underground Dict. (1972).
1979		G. Swarthout Skeletons 216: I think you are a joto. A queer. And a coward.
1992		Bentley & Corbett Prison Sl. 53: Joto A homosexual. Although joto is used to mean any homosexual, it is primarily used in reference to the passive partner in a homosexual relationship.
2000		Other Side of the Wall: Prisoner’s Dict. July 🌐 Joto: Homosexual, punk. (Sp., TX).