elongate vs lengthen

elongate

verb
  • To make long or longer by pulling and stretching; to make elongated. 

  • To become long or longer by being pulled or stretched; to become elongated. 

adj
  • Lengthened, extended, elongated; relatively long and slender. 

lengthen

verb
  • To make longer, to extend the length of. 

  • To become longer. 

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