such-and-such vs unfamiliar

such-and-such

noun

  • A placeholder or generic thing. 

det

  • indefinite; some or other, not stated 

unfamiliar

noun

  • An unfamiliar person; a stranger. 

adj

  • Strange, not familiar. 

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