ultra- vs under-

ultra-

prefix
  • Greater than normal quantity or importance, as in ultrasecret. 

  • Excessively, to an extreme, as in ultramicroscopic, ultra-careful. 

  • Beyond, outside of, as in ultrasonic. 

  • intensely, extremely, or exceptional 

  • Beyond, on the far side of, as in ultraviolet. 

under-

prefix
  • Behind 

  • Beneath, under 

  • Subordinate to 

  • Deficient, below what is correct 

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