1911 Encyclopædia Britannica/Emeritus

EMERITUS (Lat. from emereri, to serve out one’s time, to earn thoroughly), a term used of Roman soldiers and public officials who had earned their discharge from the service, a veteran, and hence applied, in modern times, to a university professor (professor emeritus) who has vacated his chair, on account of long service, age or infirmity, and, in the Presbyterian church, to a minister who has for like reason given up his charge.