thence vs thereof

thence

adv
  • Deriving from this fact or circumstance; therefore, therefrom. 

  • From there, from that place or from that time. 

thereof

adv
  • From that circumstance or origin; therefrom, thence. 

  • Of this, that, or it. 

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