a blow on the ear.

    1605 Shakespeare London Prodigal B3: If it were not vor shame, chee would a giuen thee zutch a whister poope vnder the eare. 1818 W. Scott Heart of Mid-Lothian (1883) 328: I redd thee keep hand off her, or I'se lend thee a whisterpoop. 1890–1904 Farmer & Henley Sl. and Its Analogues VII 340/1: Whister-clister (Whister-snefet, Whister-snivet, Whister-twister, or Whister-poop) […] a thumping blow; spec. a back-handed blow.

wisty-castor n. (also whisty-castor) [var. on whister-clister n.]

a punch, a blow.

    1823 Egan Grose's Classical Dict. of the Vulgar Tongue n.p.: wisty castors Heavy blows given by scientific pugilists, tending to take the fight out of each other. 1832 Egan Bk of Sports 202: Neal […] now and then put in a whisty-castor, which rather changed the look of Sam's frontispiece.