cumulate vs unpile

cumulate

noun
  • An igneous rock formed by the accumulation of crystals from a magma either by settling or floating. 

adj
  • accumulated, agglomerated, amassed 

verb
  • To accumulate; to amass. 

  • To be accumulated. 

unpile

verb
  • To remove from a pile or stack. 

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