crock 3 
(kr
ŏk)
Chiefly British Slang n. One that is worn-out, decrepit, or impaired; a wreck.
v. crocked, crock·ing, crocks
v.intr. To become weak or disabled. Often used with up.
v.tr. To disable; wreck. Often used with up.
[Earlier, old ewe that has ceased bearing; probably akin to Norwegian krake, sickly animal, and Middle Dutch kraecke, broken-down horse.]