flap vs vowel

flap

noun
  • A consonant sound made by a single muscle contraction, such as the sound /ɾ/ in the standard American English pronunciation of body. 

  • A side fin of a ray. 

  • The motion of anything broad and loose, or a sound or stroke made with it. 

  • Anything broad and flexible that hangs loose, or that is attached by one side or end and is easily moved. 

  • A piece of tissue incompletely detached from the body, as an intermediate stage of plastic surgery. 

  • A hinged leaf. 

  • The labia, the vulva. 

  • A hinged surface on the trailing edge of the wings of an aeroplane, used to increase lift and drag. 

  • A controversy, scandal, stir, or upset. 

verb
  • To move loosely back and forth. 

  • To move (something broad and loose) up and down. 

  • Of a resource or network destination: to be advertised as being available and then unavailable (or available by different routes) in rapid succession. 

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 flap and vowel occurred in a corpus of books? (source: Google Ngram Viewer )