slave-girl vs vassal

slave-girl

noun
  • A female required to perform sexual acts, a sex slave. 

  • A female slave. 

vassal

noun
  • Any direct subordinate bound by such vows to a superior. 

  • The grantee of a fief, a subordinate granted use of a superior's land and its income in exchange for vows of fidelity and homage and (typically) military service. 

  • Any subordinate bound by similar close ties. 

adj
  • Resembling a vassal; slavish; servile. 

verb
  • To treat as a vassal or to reduce to the position of a vassal; to subject to control; to enslave. 

  • To subordinate to someone or something. 

How often have the words slave-girl and vassal occurred in a corpus of books? (source: Google Ngram Viewer )