ergo vs herefor

ergo

adv
  • Consequently, therefore, or thus. 

conj
  • therefore (especially in syllogisms) 

noun
  • An ergonomic factor or characteristic. 

herefor

adv
  • For this: instead or in consideration of this, with a view to this. 

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