dig, n.⁵ — Green’s Dictionary of Slang

dig n.⁵

[? dig v.³, i.e. something one studies closely or enjoys]

(US) a sex show.

1935		A.J. Pollock Und. Speaks 31/1: Dig, a lewd act.
1939		D. Maurer ‘Prostitutes and Criminal Argots’ in Lang. Und. (1981).
1941		G. Legman ‘Lang. of Homosexuality’ Appendix VII in Henry Sex Variants.
1965		Guild Dict. Homosexual Terms 11: dig (n.): A sexual exhibition. (Slang.).