disunite vs sunder

disunite

verb
  • To separate, sever, or split. 

  • To cause disagreement or alienation among or within. 

  • To disintegrate; to come apart. 

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 disunite and sunder occurred in a corpus of books? (source: Google Ngram Viewer )