sergeant: [12] A sergeant is etymologically simply a ‘servant’ – and indeed that is what the word originally meant in English. It comes via Old French sergent from Latin servient-, the present participial stem of servīre ‘serve’. It was subsequently incorporated into the terminology of the feudal system, roughly equivalent in application to esquire, and it was also used for various legal officers, but it does not seem to have become a specific military rank until the mid 16th century. ‘Sergeant’ then was a comparatively exalted position, but by the end of the century we see it settling into its modern niche as a senior noncommissioned officer. => servant, serve
