according to W3(unab.), a cosh is a British blackjack..

Etymology: perhaps from Romany kosh, koshter stick, skewer
chiefly Britain : a weighted weapon usually similar to a blackjack; also : an attack with a cosh

as for blackjack (ca. 1889), from the same source..

[black + jack (instrument)] : a small striking weapon typically consisting at the striking end of a leather-enclosed piece of lead or other heavy metal and at the handle end of a strap or springy shaft that increases the force of impact

Last edited by tsuwm; 12/06/08 10:56 PM.