melanoid vs stygian

melanoid

noun

  • Synonym of melanoidin 

adj

  • Relating to, or afflicted with, melanosis. 

  • Relating to, or resembling, melanin. 

stygian

adj

  • Having a luminosity below 0%. 

  • Dark and gloomy. 

  • Infernal or hellish. 

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