Incidentally, Norwegian for butterfly is also sommerfugl, but in Swedish, it’s fjäril. I wonder why? Those languages tend to correlate.
Probably the former - the Hebrew word for butterfly is “parpar”, and Hebrew and Arabic have a lot of common roots.
You’ve only misled him/her about the spelling of misled. 
I’d stand corrected, but I already knew. I was looking at it forlornly, after the edit window closed, thinking, “Damn, that shouldn’t have an ‘a’ in it”!
I agree. Likewise, the theories that “butterfly” is somehow related to the colour of that insect’s excrement. I can’t say I’ve particularly noticed butterfly droppings more than the other types of animal poo that I have encountered as I go about my daily business, but I do note that many other animals seem to excrete matter that has a whitish hue. Why not “buttercats” and “butterfrogs”, then?
Wait a minute. I poorly expressed myself. What I wrote about “farfalla” wasn’t based on any actual informations I had, but was a WAG based on similarities with other words and a quick look at the etymology of these words.
And the Italian derived from Arabic word I mentioned referred to fantastic creatures, not to butterflies, hence in all likehood has no relationship altogether with the Hebraic word for “butterfly”.
To sum up, it’s better to ignore my comment about “farfalla” that I pulled out of thin air.
I am beginning to agree that sound is probably not correct as the source of the words for butterfly in various languages.
However, it is still interesting, and I’ve seen it commented on in books on language, that it varies more than most words do among languages that are otherwise closely related.
Ed
It seems like in general insect names are more subject to regional variation than other words. I can think of sever insects that have several names in the the United States alone.
Could this be because children have more interest in insects than adults, so childish names stick and local variations stay intact, much like how childhood rhymes will vary across regions?