enfranchisement vs manumission

enfranchisement

noun
  • A release from slavery 

  • The investiture with any of several municipal privileges 

  • the conversion of a copyhold estate into a freehold estate 

  • The act of enfranchising 

manumission

noun
  • Release from slavery or other legally sanctioned servitude; the giving of freedom; the act of manumitting. 

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