apportion vs split up

apportion

verb
  • To divide and distribute portions of a whole. 

  • Specifically, to do so in a fair and equitable manner; to allocate proportionally. 

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 apportion and split up occurred in a corpus of books? (source: Google Ngram Viewer )