servant (n.)youdaoicibaDictYouDict[servant 词源字典]
c. 1200, "personal or domestic attendant," from Old French servant "servant; foot-soldier," noun use of servant "serving, waiting," present participle of servir "to attend, wait upon" (see serve (v.)).

Meaning "professed lover, one devoted to the service of a lady" is from mid-14c. In North American colonies and U.S., the usual designation for "slave" 17c.-18c. (in 14c.-15c. and later in Biblical translations the word often was used to render Latin servus, Greek doulos "slave"). Public servant is attested from 1670s.[servant etymology, servant origin, 英语词源]