earthly vs unheard-of

earthly

noun
  • That which is of the earth or earthly; a terrestrial being. 

  • A slightest chance (of success etc.) or idea (about something). 

adv
  • in an earthly manner. 

adj
  • Used for emphasis 

  • Relating to the earth or this world, as opposed to heaven; terrestrial. 

unheard-of

adj
  • Unknown or known to only few people. 

  • Previously unknown; unprecedented. 

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