kvetching vs sullen

kvetching

noun

  • Persistent complaining. 

sullen

noun

  • Sullen feelings or manners; sulks; moroseness. 

adj

  • Having a brooding ill temper; sulky. 

  • Gloomy; dismal; foreboding. 

  • Sluggish; slow. 

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