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 to careful examination" (as of an animal by a veterinarian, especially of a horse before a race) is first attested 1904, in Kipling. Related: Vetted; vetting.
vet (n.2) Look up vet at Dictionary.com
1848, shortened form of veteran.