concomitance vs simultaneousness

concomitance

noun
  • occurrence or existence together or in connection with one another, coexistence 

  • A concomitant. 

  • The Roman Catholic doctrine of the existence of the entire body of Christ in the Eucharist, under each element, so that the body and blood are both received by communication in one kind only. 

simultaneousness

noun
  • The quality or state of being simultaneous; simultaneity. 

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