Here's how the evolution likely happened:
1. Veterinarian: This term, referring to a doctor for animals, originated from the Latin word "veterinarius" which means "pertaining to beasts of burden".
2. Vet: This became a common abbreviation for "veterinarian", used in everyday speech and writing.
3. Vetting: The verb "vet" started being used figuratively to mean "to examine or scrutinize thoroughly", likely drawing a parallel to the meticulous examination veterinarians perform on animals. This usage emerged in the mid-20th century and became increasingly common in the latter half.
So, the next time you're "vetting" a job candidate, remember the word's roots in the thorough examination performed by animal doctors.