nah vs not really

nah

intj
  • here! (when giving something). 

  • No. 

not really

adv
  • To a low degree, not particularly, not especially. 

  • Not actually (a hypothetical will not, in fact, come to pass), often rhetorical. 

How often have the words nah and not really occurred in a corpus of books? (source: Google Ngram Viewer )