blackamoor vs obsidian

blackamoor

noun
  • A stylized Negro. 

  • A blackamoor slave, a blackamoor servant; and hence any slave, servant, inferior, or child. 

obsidian

noun
  • A slightly bluish black, the color of obsidian glass. 

  • A type of naturally occurring black glass produced by volcanoes. 

adj
  • black 

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