continuant vs unflappable

continuant

adj
  • Continuing; prolonged; sustained. 

noun
  • An endurant. 

  • A determinant formed from a tridiagonal matrix. 

  • A linguistic sound other than a stop. 

unflappable

adj
  • Remaining composed and level-headed at all times; impossible to fluster; not becoming frustrated or irritated easily. 

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