mantelpiece vs mantelshelf

mantelpiece

noun
  • A shelf that is affixed to the wall above a fireplace. 

mantelshelf

noun
  • A shelf above a fireplace. 

  • A maneuver to surmount a ledge, involving pushing down on the ledge to bring up the body. 

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