Why are they called butterflies? They are neither flies nor butter. I think a better name would be flutterbys.

I did a search on "butterfly entymology" and found the below to copy:

The Oxford English Dictionary notes some old Dutch words “botervlieg” and “boterschijte,” and conjectures that butterflies’ excrement may have been thought to resemble butter, hence giving the name “butter-shit,” then “butter-fly”.

Webster’s Third New International Dictionary says perhaps the word comes from the notion that butterflies, or witches in that form, stole milk and butter

maybe someone thought they were flies and butter

Why do we drive on the parkway and park on the driveway?  Life is just full of mysteries.  

Or "AEROPILLAR."

Sometimes they are called "A big stain on the windshield" :)