What is the meaning of the word "xanthic acid"?

Definitions:

  1. A carbonic acid derivative, known for its ability to form salts called xanthates when it reacts with metallic hydroxides. copy to clipboard NOUN
  2. A colorless, unstable, oily thio acid, obtained by reacting potassium ethoxide with carbon disulfide. copy to clipboard NOUN
  3. Any of a class of unstable organic acids containing sulphur. copy to clipboard NOUN