extend vs open up

extend

verb
  • To increase in extent. 

  • To reenlist for a further period. 

  • To increase in quantity by weakening or adulterating additions. 

  • To value, as lands taken by a writ of extent in satisfaction of a debt; to assign by writ of extent. 

  • To straighten (a limb). 

  • Of a class: to be an extension or subtype of, or to be based on, a prototype or a more abstract class. 

  • To cause to increase in extent. 

  • To cause to last for a longer period of time. 

  • To possess a certain extent; to cover an amount of space. 

  • To bestow; to offer; to impart; to apply. 

open up

verb
  • To widen. 

  • Synonym of cheat out (“to face or turn toward the audience more than would be natural”) 

  • To begin running, driving, travelling, etc., at maximum speed. 

  • To commence firing weapons. 

  • To rain. 

  • To open. 

  • To reveal oneself; to share personal information about oneself; to become communicative. 

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