such-and-such vs undiscovered

such-and-such

det

  • indefinite; some or other, not stated 

noun

  • A placeholder or generic thing. 

undiscovered

adj

  • That has not been discovered; unknown. 

  • That has not yet been discovered; unexplored. 

How often have the words such-and-such and undiscovered occurred in a corpus of books? (source: Google Ngram Viewer )