Elaine Smith, ‘From Floon or Fleen to NYC: Symbolic sound demystified’, http://www.utm.utoronto.ca/main-news/floon-or-fleen-nyc-symbolic-sound-demystified, University of Toronto Mississauga (April 18, 2016).

ee & oo

People intuitively associate front vowel sounds – those produced with the tongue relatively far forward in the mouth, such as the ee in feet — with things that are close by. Conversely, they relate back vowel sounds – those produced with the tongue far back in the mouth, such as oo in food – to things that are farther away. (…) The study is a significant addition to the existing body of knowledge about sound symbolism. (…) Feelings and intuitions about sounds (…) have currency.