verb
1 knock with the knuckles of a hand on a door or window to attract attention: ...because his wife was chapping at my door looking for him ... la16-.
2 mash (vegetables): And you’d boil that [a swede] and then chap it up and make a poultice. 18-.
noun a knock on a door: And anither chap comes, louder, at the door. 16-. Compare champ etymology: Scots; origin obscure but perhaps from Middle English chapp-en, Middle Dutch kappen, Low German. Middle High Gernan, Middle Swedish kappa, Middle Danish kappe; sense 1 attested by SR, JS, SS, ET, BW, DW and WM in DB; noun and verb attested by AS and BS in TDITA