residuum vs scoria

residuum

noun
  • The residue, remainder or rest of something. 

  • The residue of an estate. 

  • The solid material remaining after the liquid in which it was dissolved has been evaporated; a residue. 

  • A binary function from [0,1] × [0,1] to [0,1] which is defined in terms of the t-norm as follows: x→y= sup z|z*x⩽y, where * denotes the t-norm function and sup denotes the supremum. 

scoria

noun
  • The slag or dross that remains after the smelting of metal from an ore. 

  • Rough masses of rock formed by solidified lava, and which can be found around a volcano's crater. 

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