"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.
Proto-Indo-European root meaning "dog."
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit svan-, Avestan spa, Greek kyōn, Latin canis, Old English hund, Old High German hunt, Old Irish cu, Welsh ci, Russian sobaka (apparently from an Iranian source such as Median spaka), Armenian shun, Lithuanian šuo "dog."