offsplit vs sunder

offsplit

verb
  • To split off; secede. 

noun
  • A splitting off or breaking away from; a secession; divergence. 

sunder

verb
  • To part, separate. 

  • To break or separate or to break apart, especially with force. 

noun
  • a separation into parts; a division or severance 

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