cut the muster/cut the mustard
Some people insist that the original phrase is “cut the muster” rather than the seemingly nonsensical “cut the mustard.” This etymology seems plausible at first. Its proponents often trace it to the American Civil War. We do have the analogous expression “to pass muster,” which probably first suggested this alternative; but although the origins of “cut the mustard” are somewhat obscure, the latter is definitely the form used in all sorts of writing throughout the 20th century. No advocate of the rival form has ever documented an authentic instance of its use in a 19th-century context. Common sense would suggest that a person cutting a muster is not someone being selected as fit, but someone eliminating the unfit.