exterior vs on the surface

exterior

noun

  • Foreign lands. 

  • The outside part, parts or surface of something. 

adj

  • Being from outside a country; foreign. 

  • Outdoor. 

  • Relating to the outside parts or surface of something. 

on the surface

prep

  • apparently, outwardly; superficially 

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