From the story about foxhunting in Ethiopia:
"Chastised with what?" he said.

"With the kourbash--on the feet. A kourbash is a strip of old hippo-hide with a sort of keel on it, like the cutting edge of a boar's tusk. But we use the rounded side for a first offender."

Effects of the kourbash:
""And do any consequences follow this sort of thing? For the victim, I mean--not for you?"

Ve-ry rarely. Let me be fair. I've never seen a man die under the lash, but gangrene may set up if the kourbash has been pickled."

"Pickled in what?" All the table was still and interested.

"In copperas, of course. Didn't you know that" said the Inspector.

"Thank God I didn't." The large man sputtered visibly."

I'm pretty sure copperas is copper sulfate, which should
kill bacteria on the kourbash. I think a "not" was omitted.

I suspect that the copperas used in this instance was a form of ferrous sulphate, commonly used to tan leather, which leads to the guess that the pickling in question was actually tanning.

Dear Father Steve: Thank you for correcting my error. Appearances can be deceiving, especially with words.
Webster's 1913 Dictionary

Definition: \Cop"per*as\, n. [OE. coperose, F. couperose, fr.
(assumed?) L. cuprirosa, equiv. to G. cha`lkanqos, i. e.
copper flower, vitriol. See {Copper} and {Rose.}]
Green vitriol, or sulphate of iron; a green crystalline
substance, of an astringent taste, used in making ink, in
dyeing black, as a tonic in medicine, etc. It is made on a
large scale by the oxidation of iron pyrites. Called also
{ferrous sulphate}.

Note: The term copperas was formerly synonymous with vitriol,
and included the green, blue, and white vitriols, or
the sulphates of iron, copper, and zinc.

Clever and resourceful people made this stuff near London at one time ... it figures in an English novel which I cannot now recall.