Green’s Dictionary of Slang

sexual petting (and intercourse), esp. in a dark cinema.

1984		Partridge DSUE (8th edn) 384/2: since 1945.
1989		T. Blacker Fixx 180: Down boy [...] Feelies are for upstairs.
1993		R. Shell Iced 45: To hang out and sneak feelies and kisses with the girlies.