accumulate vs buy up

accumulate

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

  • To gradually grow or increase in quantity or number. 

adj
  • Collected; accumulated. 

buy up

verb
  • To buy the whole of; to purchase the entire stock of something. 

  • To buy off; to pay in blackmail money or similar. 

  • To buy whatever is available of something. 

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