once vs whereupon

once

conj
  • As soon as; when; after. 

adv
  • Multiplied by one: indicating that a number is multiplied by one. 

  • One and only one time. 

  • Formerly; during some period in the past. 

whereupon

conj
  • After which, in consequence. 

  • Upon which. 

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