pileup vs thud

pileup

thud

verb

  • To make the sound of a dull impact. 

noun

  • The sound of a dull impact. 

  • A slower, dull impact with a wide surface area. 

  • A hard, dull impact. 

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