The noun butterfly, which appeared around the year 1000 as buttorfleoge, is simply a compound of butter and fly, and not — as sometimes poetically suggested — an alteration of flutter by.
This name is unexplained. Dutch had botervlieg and German Butterfliege, which, like the English name, literally meant butter-fly (German even had Buttervögel, butter-bird).
One obsolete Dutch name, boterschijte, suggests that the insect was named after the appearance of its excrement (schijt = shit). But the usual German name is Schmetterling, from dialectal Schmetten, cream, from Czech smetana, of same meaning, and German also used Botterlicker, butter-licker, Molkendieb and Molkenstehler, whey-thief, and Milchdieb, milk-thief. It has been said that these names reflect the popular beliefs that the butterfly, or elves or witches in its shape, stole milk and butter. These legends themselves, however, may have arisen out of the names, which, according to some, originally referred to the smooth, ‘creamy’ feel of the fine ‘dust’ of the wings, or more simply and more probably to the colour of the commonest varieties of butterflies.
French uses papillon and Catalan papallona, from Latin pāpĭlĭo/ōnis, butterfly, moth, a formation with reduplication of p perhaps expressive of the fluttering sound made by a butterfly or moth. (Incidentally, pāpĭlĭo came to be used in the sense of tent, hence French pavillon and English pavilion.)
The Germanic languages had similar expressive formations with reduplication of f: Old English fīfalde, Old Saxon fīfoldara, Old High German fīfaltra, Old Icelandic fífrildi and dialectal Swedish feffel all had the sense of butterfly.
The initial p- of Latin pāpĭlĭo, corresponding to the initial f- of these Germanic words illustrates Grimm’s Law*. This law is the observation that certain Indo-European consonants (mainly stops) undergo regular changes in the Germanic languages which are not seen in others such as Greek or Latin. One of the examples is p- becoming f-, as in:
– Latin păter/tris and French père, corresponding to English father and Swedish fader
– Latin pēs/pĕdis and Portuguese pé, corresponding to English foot and German Fuss
– French poisson and Romanian peşte, corresponding to English fish and German Fisch.
(* set out by the German philologist and folklorist Jacob Grimm (1785-1863) in his German grammar – 2nd edition, 1822)
According to Santiago Segura Munguía (1922-2014) in Lexicón [incompleto] etimológico y semántico del Latín y de las voces actuales que proceden de raíces latinas o griegas (2014), the Spanish name mariposa is from María, pósate!, Mary, alight!, a child’s expression similar to María vola, Mary fly away, used in the same sense in Sardinia and in central France. (Similarly, Spanish mariquita means ladybird.)
The origin of the Portuguese name borboleta is disputed. Some say that it is from a Late-Latin form papillitta, from pāpĭlĭo, others that it is from a Late-Latin form belbellita, from bellus, pretty, handsome, charming, pleasant, etc.
The Italian name farfalla is of uncertain origin; it might be based on Latin pāpĭlĭo or simply be an expressive formation. (English has borrowed the plural farfalle in the sense of small pieces of pasta shaped like butterflies’ wings.)
Also of uncertain origin, the Romanian name fluture is perhaps related to German flattern, to flutter, and Falter used in Tagfalter, butterfly, and Nachtfalter, moth. (German Tag and Nacht mean day and night; likewise, French papillon de nuit, literally night’s butterfly, means moth.)