echoic vs onomatopoeic

echoic

adj
  • Imitative of a sound; onomatopoeic. 

  • Of or pertaining to an echo 

onomatopoeic

adj
  • Of or relating to onomatopoeia. 

  • Having the property of onomatopoeia. 

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