late 14c., agent noun from thresh. The thresher shark (c. 1600) so called for its long upper "tail," which resembles a threshing tool. The Greek for it was alōpēx, literally "fox," also for the tail.
"something that strongly attracts attention," 1590s, from French cynosure (16c.), from Latin Cynosura, literally "dog's tail," an old name of the constellation (now Ursa Minor) containing what is now (but was not in ancient times) the North Star, the focus of navigation, at the tip of its tail; from Greek kynosoura, literally "dog's tail," from kyōn (genitive kynos; from PIE root *kwon- "dog") + oura "tail" (see arse). Apparently in ancient times the whole constellation was used as a rough indicator of the celestial north pole. Related: Cynosural.
"passage added to a musical composition for the purpose of bringing it to a conclusion," 1753, from Latin cauda "tail of an animal," which is of uncertain origin. De Vaan traces it to Proto-Italic *kaud-a- "part; tail," from PIE *kehu-d- "cleaved, separate," from root *khu-. He writes: "Since words for 'piece, part' are often derived from 'to cut, cleave', the tail may have been referred to as the loose 'part' of the animal."
The bushy tail also inspired words for "fox" in Welsh (llwynog, from llwyn "bush"); Spanish (raposa, from rabo "tail"); and Lithuanian (uodegis, from uodega "tail"). Metaphoric extension to "clever person" was in late Old English. Meaning "sexually attractive woman" is from 1940s; but foxy in this sense is recorded from 1895. A fox-tail was anciently one of the badges of a fool (late 14c.).
A late Old English translation of the Medicina de Quadrupedibus of Sextus Placitus advises, for women "who suffer troubles in their inward places, work for them into a salve a foxes limbs and his grease, with old oil and with tar; apply to the womens places; quickly it healeth the troubles." It also recommends, for sexual intercourse without irritation, "the extremest end of a foxes tail hung upon the arm." Rubbing a fox's testicles on warts was supposed a means to get rid of them.
Proto-Indo-European root meaning "to turn, vacillate, tremble ecstatically."
It is the hypothetical source of/evidence for its existence is provided by: Latin vibrare "set in tremulous motion, move quickly to and fro, quiver, tremble, shake," Lithuanian vyburti "to wag" (the tail), Danish vippe, Dutch wippen "to swing," Old English wipan "to wipe."