pairing vs simultaneity

pairing

noun
  • The combination or union of two things. 

  • An agreement between two members of a legislative body holding opposite opinions to refrain from voting, so that both may absent themselves. 

simultaneity

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

  • More than one complete musical texture occurring at the same time. This first appeared in the music of Charles Ives, and is common in the music of Conlon Nancarrow, and others. 

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