In English butterflies are so called because their shit looks like butter...not because the name is a mispronunciation of 'flutter by.' In most other languages the word has a completely different origin though.
In Russian the origin of the word is 'peasant woman' or 'grandmother' The same word is also used for 'bow tie.' Several Romance languages use variations of the original Latin 'papilio' which also had the meaning of 'tent.' This is where the word 'pavilion' comes from.
A butterfly is known as a 'summer fly' or even a 'summer bird' in various Germanic languages. and in ancient Greek the word for 'butterfly' was the same as 'soul,' but in Modern Greek butterflies are 'petals.'