Q From Jerzy Wawro: Some years ago I came across an article about a zoo and its new acquisition, a lion. The zoo had hoped to gain cubs, but this lion, as the newspaper informed me, was unable to cut his mustard. What has mustard got to do with it? Is there a good story behind this expression or is it just one of those enduring nonsenses?
A It seems that the phrase is of early twentieth-century US origin. The first recorded use of the phrase is by O Henry in 1907, in a story called The Heart of the West: “I looked around and found a proposition that exactly cut the mustard”. The modern sense of the idiom is “to succeed; to have the ability to do something; to come up to expectations”. But why that exact phrase, nobody seems to know. Cutting mustard is hardly an arduous endeavour, after all, and there seems not to be any older phrase to which it is related.
One explanation that is sometimes given is that the phrase is a corrupted form of cut the muster, in some way connected with the military muster or assembly of troops for inspection. However, if you cut a muster, presumably you do not attend it, so how this can be connected with the idea of excellence is far from clear. The clinching argument for this not being the source is that nobody has found the supposedly original phrase cut the muster anywhere.
It’s much more likely that it’s a development of the long-established use of mustard as a superlative, as in phrases such as keen as mustard. In the nineteenth century in America, mustard was used figuratively to mean something that added zest to a situation, and the proper mustard was something that was the genuine article. The move from genuine to excellent is just a short step. O Henry used the word in the sense of something excellent in Cabbages and Kings in 1904: “I’m not headlined in the bills, but I’m the mustard in the salad dressing just the same”.
But how the idea of cutting the mustard became included are not known.
As I can’t fully answer your question, let me present as a consolation prize the reason why mustard is so named. It derives from an ancient French way of making a hot condiment by grinding up the seeds of various members of the cabbage family in the freshly pressed juice of grapes, then called the moust (must in modern English). A French word moustarde appeared to describe this mixture, which was brought into English in the twelfth century and quickly settled to the modern spelling. (Luckily moust and moustarde shifted their spelling and pronunciation in the same direction down the years, so their connection is still obvious.)