vet (n.1) Look up vet at Dictionary.com
1862, shortened form of veterinarian.
vet (v.) Look up vet at Dictionary.com
"to submit (an animal) to veterinary care," 1891, from veterinarian. The colloquial sense of "subject (something) to careful examination" (as of an animal by a veterinarian, especially of a horse before a race) is attested by 1901. Related: Vetted; vetting.
vet (n.2) Look up vet at Dictionary.com
1848, shortened form of veteran (n.).