In many languages, front vowels are used in words for small, thin, light things, and back vowels in words for big, fat, heavy things. It’s not always true, but it’s a tendency that you can see in the stressed vowels in words like little, teeny or itsy-bitsy (all front vowels) versus humongous or gargantuan (back vowels). Or in Spanish, chico (“small,” front vowel) versus gordo (“fat,” back vowel). Or French petit (front vowel) versus grand (back).
One marketing study at Loyola College created pairs of made-up product names that were identical except for having front or back vowels and asked participants to answer:
Which brand of laptop seems bigger, Detal or Dutal?
Which brand of vacuum cleaner seems heavier, Keffi or Kuffi?
Which brand of ketchup seems thicker, Nellen or Nullen?
In each case, the product named with back vowels (Dutal, Kuffi, Nullen) was chosen as the larger, heavier, thicker product.
Full story here, including why we tend to speak in high pitches to babies and some evidence that this is taken into account by companies naming ice cream flavors and crackers.