bondage vs vassalage

bondage

noun
  • The state of being enslaved or the practice of slavery. 

  • The practice of physically restraining people for sexual pleasure, such as by tying up or shackling. 

  • Applied to clothing with many buckles, zips, etc., associated with punk and goth subcultures. 

  • The state of lacking freedom; constraint. 

vassalage

noun
  • The state of being a vassal. 

How often have the words bondage and vassalage occurred in a corpus of books? (source: Google Ngram Viewer )