Green’s Dictionary of Slang

of a man, to have sexual intercourse; thus foining n., having sexual intercourse.

1593		Nashe Choise of Valentines (1899) 13: And then he flue on hir as he were wood, And on hir breeche did hack and foyne a-good.
c.1597		Shakespeare Henry IV Pt 2 II i: If his weapon be out: he will foin like any devil. [Ibid.] II iv: Thou whoreson little tidy Bartholomew boar-pig, when wilt thou leave fighting o’ days, and foining o’ nights, and begin to patch up thine old body for heaven?
1618		Fletcher Loyal Subject I iv: Into what Grooms Feather-Bed will you creep now? And there mistake the enemy; sweet youths ye are, And of a constant courage; are you afraid of foyning?
1621		Beaumont & Fletcher Thierry and Theodoret II i: Goe get you to your foyning work at Court, And learn to sweat again, and eat dry mutton.