emeritus

In Latin, emeritus was used to describe soldiers who had completed their duty. It is the past participle of the verb emereri, meaning "to serve out one's term," from the prefix e-, meaning "out," and merēre, "to earn, deserve, or serve." (Merēre is also the source of our word merit.) English speakers claimed emeritus as their own in the late 17th century, applying it as both a noun and an adjective referring or relating not to soldiers but to someone who is retired from professional life but permitted to keep as an honorary title the rank of the last office they held. The adjective is frequently used postpositively—that is, after the noun it modifies rather than before it—and it is most commonly used to describe specifically those retired from a professorship.