posted 10-27-2008 07:47 AM                  

It's a figurative contraction of veterinarian—the fancy word for animal doctor originated in the mid-17th century. The colloquial abbreviation dates to the 1860s; the verb form of the word, meaning "to treat an animal," came a few decades later—according to the Oxford English Dictionary the earliest known usage is 1891—and was applied primarily in a horse-racing context. ("He vetted the stallion before the race," "you should vet that horse before he races," etc.) By the early 1900s, vet had begun to be used as a synonym for evaluate, especially in the context of searching for flaws.