on the surface vs unlikely

on the surface

prep
  • apparently, outwardly; superficially 

unlikely

adv
  • In an improbable manner. 

adj
  • Not holding out a prospect of success; likely to fail; unpromising. 

  • Not likely; improbable; not to be reasonably expected. 

noun
  • Something or somebody considered unlikely. 

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