prorate vs split up

prorate

verb
  • To divide proportionately, especially by day; to divide pro rata. 

split up

verb
  • separate, disassociate, cause to come apart. 

  • Cease to be together, break apart from the group. 

adj
  • Divided or separated. 

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