The vowels have always been linked to the seven heavens, most famously in Hebrew, where the seven unwritten vowels created the sound for God—Jehovah. The link between the language of man and the presumed languages of the seven Heavenly spheres has always been speculated upon. However, it is one of the more arcane secrets of the mystics which of the seven planets is linked to which vowel.”
Excerpted from: Rogerson, Barnaby. Rogerson’s Book of Numbers: The Culture of Numbers–from 1,001 Nights to the Seven Wonders of the World. New York: Picador, 2013.