fluctuant vs vacillant

fluctuant

adj
  • That fluctuates or causes fluctuation. 

  • Used to describe a fluid-filled structure, such as an abscess, that produces a wave-like motion when palpated. 

vacillant

adj
  • Vacillating; wavering; fluctuating; irresolute. 

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