Green’s Dictionary of Slang

(US black) a promiscuous woman, one who openly seeks sex.

1933		Curley Weaver ‘You Was Born to Die’ 🎵 Don’t want no woman to run around, / Stay out in the street, act like a fanfoot clown.
1942		Z.N. Hurston Dust Tracks On a Road (1995) 693: Fan-foot, what you doing with my man’s hat cocked on your nappy head? [...] Yeah I sleeps with my men, but they pays me. I wouldn’t be a fan-foot like you.
1948		Z.N. Hurston Seraph on the Suwanee (1995) 744: What do Jim mean by listening to all that rigmarole from that fan-foot, the street-walker, that brick-bat for?
1960		V. Williams Walk Egypt 282: She said instantly, fiercely, ‘Fan-Foot Alley can miss you this trip.’ [DARE].
1969		Skip James in Levet Talkin That Talk (2010) 161/2: Now that type of barrelhouse or no-good woman is called a sandfoot or fanfoot. That’s the type of woman that don’t have no special man and don’t care whether she see him again since she can get what she got.