reunify vs split up

reunify

verb
  • To unify again; to bring back together, or come back together, after separation. 

split up

adj
  • Divided or separated. 

verb
  • separate, disassociate, cause to come apart. 

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

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