late 14c., Pliades, "visible open star cluster in the constellation Taurus," in Greek mythology they represent the seven daughters of Atlas and Pleione, transformed by Zeus into seven stars. From Latin Pleiades, from Greek Pleiades (singular Plēias), perhaps literally "constellation of the doves" from a shortened form of peleiades, plural of peleias "dove" (from PIE root *pel- "dark-colored, gray"). Or perhaps from plein "to sail," because the season of navigation begins with their heliacal rising.
Old English had the name from Latin as Pliade. The star cluster is mentioned by Hesiod (pre-700 B.C.E.); only six now are visible to most people; on a clear night a good eye can see nine (in 1579, well before the invention of the telescope, the German astronomer Michael Moestlin (1550-1631) correctly drew 11 Pleiades stars); telescopes reveal at least 500. Hence French pleiade, used for a meeting or grouping of seven persons.