disapprove vs frown on

disapprove

verb
  • To condemn; to consider wrong or inappropriate; used with of. 

  • To have or express an unfavorable opinion. 

  • She disapproves of rap music because of its sometimes aggressive lyrics. 

  • To refuse to approve; reject. 

frown on

verb
  • To disapprove of (something or someone, often a behavior); to express disapproval of (something or someone). 

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