trill vs vowel

trill

noun
  • A type of consonantal sound that is produced by vibrations of the tongue against the place of articulation: for example, Spanish ⟨rr⟩, /r/. 

  • A rapid alternation between an indicated note and the one above it, in musical notation usually indicated with the letters tr written above the staff. 

  • A tremulous high-pitched vocal sound produced by cats. 

verb
  • To impart the quality of a trill to; to utter as, or with, a trill. 

  • To create a trill sound; to utter trills or a trill; to play or sing in tremulous vibrations of sound; to have a trembling sound; to quaver. 

adj
  • true, respected 

vowel

noun
  • A sound produced by the vocal cords with relatively little restriction of the oral cavity, forming the prominent sound of a syllable. 

  • A letter representing the sound of vowel; in English, the vowels are a, e, i, o, u, and y. 

verb
  • To add vowel points to a consonantal script (e.g. niqqud in Hebrew or harakat in Arabic). 

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