so-called vs spurious

so-called

adj
  • Commonly called by such a name, but not worthy of it. 

  • So named; commonly called. 

spurious

adj
  • Extraneous; stray; not relevant or wanted. 

  • False, not authentic, not genuine. 

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