such-and-such vs unrecognized

such-and-such

det

  • indefinite; some or other, not stated 

noun

  • A placeholder or generic thing. 

unrecognized

adj

  • Not matched in memory. 

  • Not acknowledged; not granted recognition. 

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