fixity vs permanence

fixity

noun
  • The state or condition of being fixed. 

  • The position of an operator relative to its operand (prefix, postfix) or operands (infix). 

  • Something fixed. 

permanence

noun
  • The state of being permanent. 

  • The reciprocal of magnetic inductance. 

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