lose sight of vs undersee

lose sight of

verb
  • To fail to remember; to overlook or neglect. 

  • To be no longer able to see. 

undersee

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

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

  • To look intently into; examine; inspect. 

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