Green’s Dictionary of Slang

cowskin n.

(US) a whip.

[US]H.H. Brackenridge Modern Chivalry (1937) Pt I Vol. II Bk VI 150: At the various applications of the cowskin, he had jumped, and cursed, and swore.
[US]H.H. Brackenridge Modern Chivalry (1937) Pt II Vol. II Bk III 483: Doctor Mountebank, who affected now and then to chastise him with a cow-skin, to teach him manners.
[US]T. Haliburton Clockmaker I 89: Now do, marm, find out some other place to give your cattle the cowskin.
[UK] ‘Plunder Creek’ in Bentley’s Misc. Feb. 126: You tarnation nigger! Who told you to laugh? You calkilate as I harn’t got the cowskins here.

In compounds