check up vs feel out

check up

verb
  • To seem correct or plausible; to comport with known facts; to check out (with other facts). 

  • I dropped by to check up on my friend. 

  • To verify through brief investigation or revisit for assurance that there are no problems. 

  • To verify something's accuracy. 

feel out

verb
  • To try to ascertain a person's point of view, or the nature of a situation, by cautious and subtle means. 

How often have the words check up and feel out occurred in a corpus of books? (source: Google Ngram Viewer )