As crooked as a cammock. The cammock is a piece of timber bent for the knee of a ship; a hockey-stick; a shinny-club. (Anglo-Saxon.)
“Though the cammock, the more it is bowed the better it is; yet the bow, the more it is bent the weaker it waxeth.” —Lily.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894