gallet vs spall

gallet

noun
  • A splinter of stone inserted into the wet mortar of masonry. 

verb
  • To use this masonry technique. 

spall

noun
  • A splinter, fragment or chip, especially of stone. 

verb
  • To break into fragments or small pieces. 

  • To reduce, as irregular blocks of stone, to an approximately level surface by hammering. 

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