changeable vs unflappable

changeable

adj
  • Capable of being changed. 

  • Subject to sudden or frequent changes. 

  • Capable of camouflaging itself by changing colour. 

unflappable

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

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