humid vs serous

humid

adj
  • Containing perceptible moisture (usually describing air or atmosphere); damp; moist; somewhat wet or watery. 

serous

adj
  • Containing, secreting, or resembling serum; watery; a fluid or discharge that is pale yellow and transparent, usually representing something of a benign nature. (This contrasts with the term sanguine, which means blood-tinged and usually harmful.) 

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