Green’s Dictionary of Slang

a male homosexual who taps his foot indicating a desire to make contact with another for sexual activity in a public lavatory/bathroom; thus foot-tapping n.

1967		M. Hoffman letter 2 Aug. in Humphreys Tearoom Trade 20: Men who go into a stall, close the door and then make contact with the chap in the next stall by means such as foot-tapping.
1970		R.A.L. Humphreys Tearoom Trade 65: If there are doors on the stalls, foot-tapping or note-passing may be employed.
1982		D. Huffaker Seventh East Press n.p.: [Anon. Brigham Young Uni. student] states that foot-tapping still goes on.
2007		R. Johnson N.Y. Post 18: The photos [...] do not show the fellow’s face, but the profile does feature pictures of a toe-tapper posing in various positions.
2007		Richard GLBTFT html 11 Nov. 🌐 The FT stands for Foot Tappers.
2007		Duke & Brown Wash. Post Co 1: Consider the bathroom stall, [...] it can be a world of untold secrets, codes and signals as invitations to partake. Like foot-tapping.