distend vs heighten

distend

verb
  • To extend or expand, as from internal pressure; to swell 

  • To cause to swell. 

  • To cause gravidity. 

heighten

verb
  • To advance, increase, augment, make larger, more intense, stronger etc. 

  • To make high; to raise higher; to elevate. 

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