The word "varmint" is a chiefly North American dialectal variant of "vermin," which entered English in the early 14th century from Anglo-French and Old French vermin, based on Latin vermis meaning "worm." This Latin root can be traced back to the Proto-Indo-European wr̥mis, also meaning "worm," which is the source for similar words across many languages. The specific form "varmint" emerged in the 16th century as a colloquial pronunciation, likely influenced by a regional accent that altered the middle vowel sound. Over time, it developed a distinct connotation, often used in rural or hunting contexts to refer specifically to predatory pests like foxes, weasels, or coyotes, and later extended humorously to troublesome people.

The word is a loanword and phonetic corruption of the English word "vermin." It is not productively formed from distinct, separable morphemes in its current spelling.