contrariwise vs either

contrariwise

adv
  • on the other hand 

  • in the contrary or opposite way, order, or direction 

either

adv
  • As well. 

det
  • Any one (of two). 

  • Each of two; both. 

conj
  • Introduces the first of two (or occasionally more) options or possibilities, the second (or last) of which is introduced by “or”. 

pron
  • One or the other of two people or things. 

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