Green’s Dictionary of Slang

1. (gay) a heterosexual male; also as adj.

1953		R. Garland Heart in Exile 53: I was sure he was ‘normal’.
1962		R. Hauser Homosexual Society 54: We love the body and are not ashamed of it as you squares—you Normals—are.
1972		B. Rodgers Queens’ Vernacular.
1979		Maledicta III:2 244: Heterosexuals, outsiders, jam, normals, squares, BMs (‘baby-makers,’ Cape Town), and general naph omis.
1985		B. Simon ‘Outers’ Born in the RSA (1997) 74: The hobos, the outers, the moffies [...] the kaffirs, even the normals like you.

2. see norm n. (3)