Cut the Mustard?

People use the phrase "cut the mustard" when talking about filling expectations or meeting a standard. The origin of the phrase seems a bit muddled.

Sources indicate it could mean
- Cutting the mustard plant
- Corruption of military phrase to "pass muster"
- Knife not sharp enough to cut the crust off the top of mustard in a barrel
- Diluting mustard with vinegar

Read more here, here, here, here, and here

After reading all the above references, it seems that the origin isn't really known.

Mustard plants

image Wikipedia