exo- vs under-

exo-

prefix

  • outside; external 

  • extrasolar; beyond the Solar System (our solar system) 

under-

prefix

  • Behind 

  • Beneath, under 

  • Subordinate to 

  • Deficient, below what is correct 

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