amass vs rack up

amass

verb
  • To accumulate; to assemble. 

  • to gather a great quantity of; to accumulate. 

  • To collect into a mass or heap. 

rack up

verb
  • to acquire, to gather together. 

  • to arrange in a rack 

  • to gain (points etc.; in a game or sport), to accumulate 

  • to defeat severely, to thrash 

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