check up on vs undersee

check up on

verb
  • To examine or inspect something in order to determine its condition; to check out. 

  • To look after or inquire about someone's well-being. 

undersee

verb
  • To look intently into; examine; inspect. 

  • To see or look under or below; see below the surface of. 

  • To neglect; fail to see properly or adequately; turn a blind eye to; ignore. 

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