extend vs perpetuate

extend

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

  • 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 increase in extent. 

  • To cause to increase in extent. 

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

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

perpetuate

verb
  • To prolong the existence of (something) by repetition; to reinforce. 

  • To make (something) perpetual; to make (something) continue for an indefinite time; also, to preserve (something) from extinction or oblivion. 

  • To record (the testimony of a witness) which may be lost before a matter comes to trial. 

adj
  • Perpetual, or made perpetual; continued for an indefinite time. 

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