seldom seen vs unseen

seldom seen

unseen

noun
  • An examination involving material not previously seen or studied. 

adj
  • Unskilled; inexperienced. 

  • Not hitherto noticed; unobserved. 

  • Not seen or discovered; invisible. 

How often have the words seldom seen and unseen occurred in a corpus of books? (source: Google Ngram Viewer )