英语词源字典 - 在线词源网站

doula (n.)[doula 词源字典]: by 1980, from Greek doulos (fem. doule) "slave."[doula etymology, doula origin, 英语词源]
servant (n.): 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.
dulia: "(In Roman Catholic theology) the reverence accorded to saints and angels", Late Middle English: via medieval Latin from Greek douleia 'servitude', from doulos 'slave'.
hierodule: "(In ancient times) a slave living in a temple and dedicated to the service of a god", Mid 19th century: from late Latin hierodulus, from Greek hierodoulos, from hieron 'temple' + doulos 'slave'.