occurrence vs surfacing

occurrence

noun
  • An actual instance when a situation occurs; an event or happening. 

  • The lexical aspect (aktionsart) of verbs or predicates that change in or over time. 

surfacing

noun
  • The act of coming above the surface. 

  • Material used to make a surface. 

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