quivering vs tremulous

quivering

adj

  • shaking, shivering 

noun

  • A motion by which something quivers or trembles. 

tremulous

adj

  • Trembling, quivering, or shaking. 

  • Timid, hesitant; lacking confidence. 

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