derisive vs mordacious

derisive

adj
  • Expressing or characterized by derision; mocking; ridiculing. 

  • Deserving or provoking derision or ridicule. 

noun
  • A derisive remark. 

mordacious

adj
  • Sharp in intent, sarcastic 

  • Prone to biting, aggressive (of an animal etc.). 

  • Biting, causing a physical bite or sting; corrosive 

  • sharp or caustic in style or tone. 

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