accumulate vs form drifts

accumulate

adj
  • Collected; accumulated. 

verb
  • To gradually grow or increase in quantity or number. 

  • To heap up in a mass; to pile up; to collect or bring together (either literally or figuratively) 

form drifts

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