A. To make your question more difficult, in Gen. 46:16 the same person, a son of Gad, is “Etzbon”, from etzba, a finger! “Ozni” has a connotation of hearing; “Etzbon” is derived by some lexicographers from a root that means “handsome”. The two may originally have been nicknames.
In rabbinic thinking, the mention of ears and fingers teaches a moral lesson – the finger is long and thin and the ear has a convenient opening so that if something is said that you should not listen to, a finger in your ear prevents you from hearing.