Why Butterfly?

 Why are butterflies called butterflies? It's a question I'm often asked (once my obsession becomes known) and one to which there seems to be no simple answer – or is there?
  Various theories have been advanced. One of the more plausible is that butterflies are named after the butter-yellow (or, in the male, sulphur-yellow) Brimstone, often the first butterfly to be seen in spring. Others have suggested that the name was inspired by butterflies' apparent interest in buttermilk, which does seem to attract some butterflies' attention if it's exposed in the open. There was a folk belief that witches took the form of butterflies and helped themselves to milk and butter. However, if a butterfly devoted its whole life to consuming dairy products, it would scarcely manage more than a few thimblefuls. Butterflies don't eat at all – they're not physically equipped for it; they only drink. All their eating is done at the larval stage – which makes it even stranger that some sources suggest the possibility (based on an Old Dutch word, 'boterschijte') that butterflies are so named because their excrement resembles butter. Butterflies don't excrete or egest anything, except sometimes a little water if they're overfull, so that theory sounds wildly fanciful. 
  In all this puzzlement and conjecture, did no one think to consult Johnson's Dictionary? There the curious reader will find this definition: 'A beautiful insect, so named because it first appears in the beginning of the season for butter.' The season for butter: I must admit that it had never occurred to me that there was a season for butter-making, but that was indeed the case until late in the 18th century, when changes in animal husbandry and improved breeds of cattle made milking and butter-making possible all year round. So there you have it: a butterfly is the insect that flies during the butter season – which extended roughly from March to September, as does the butterfly season. No doubt debate will continue, but it seems to me that Johnson this time got it right. The same cannot be said, however, for his definition of a caterpillar: 'A worm which, when it gets wings, is sustained by leaves and fruits.'  
  Among the most charming, if  not entirely reliable, of Johnson's animal definitions is 'Elephant': 'The largest of all quadrupeds, of whose sagacity, faithfulness, prudence, and even understanding, many surprising relations are given. He is supplied with a trunk, or long hollow cartilage, like a large trumpet, which hangs between his teeth, and serves him for hands: by one blow with his trunk he will kill a camel or a horse, and will raise a prodigious weight with it...' And I like his 'Lion': 'The fiercest and most magnanimous of four-footed beasts.' And here is 'Goldfinch': 'A singing bird, so named from his golden colour. This is called in Staffordshire a Proud Taylor.' I must remember that the next time I'm admiring the numerous goldfinches of Lichfield.