'vet' in English developed as a clipped form of two different longer words: 'veterinarian' (from French/Latin origin) and 'veteran' (from Latin). The verb sense 'to vet' (meaning to examine) originally came from the short form of 'veterinarian' in contexts of examining or treating animals; the noun 'vet' as 'veteran' is a later clipping of 'veteran'.

'veterinarian' entered English via French (vétérinaire) and Latin (veterinarius) relating to animals; it was clipped in colloquial English to 'vet' in the late 19th century, giving rise to the verb 'to vet' (originally to attend to or examine animals) and later the general sense 'to examine or screen'. 'Veteran' comes from Latin 'veteranus' (from 'vetus' meaning 'old'); the shortened noun 'vet' for 'veteran' developed through clipping in the 20th century.

Originally connected to animal care and to 'old/experienced' (from Latin roots), the shortened form 'vet' broadened: the verb moved from 'treat/examine animals' to general 'examine or screen', and the noun 'vet' came to refer both to veterinarians and to military veterans.