crasis vs mettle

crasis

noun
  • External vowel sandhi; contraction of a vowel or diphthong at the end of a word with a vowel or diphthong at the start of the following word. 

  • A mixture or combination. 

mettle

noun
  • Good temperament and character. 

  • A quality of endurance and courage. 

adj
  • Spirited, vigorous, stout-hearted. 

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