The Greek name traditionally is interpreted as "The Bearer (of the Heavens)," from a-, copulative prefix (see a- (3)), + stem of tlenai "to bear," from PIE root *tele- "to lift, support, weigh." But Beekes compares Berber adrar "mountain" and finds it plausible that the Greek name is a "folk-etymological reshaping" of this. Mount Atlas, in Mauritania, was important in Greek cosmology as a support of the heavens.
also called Laodice, a daughter of Agamemnon and Clytaemnestra, the accomplice of her brother Orestes in the murder of their mother, from Greek Ēlektra, literally "shining, bright," related to ēlektōr "the beaming sun" and perhaps to ēlektron "amber." Especially in psychological Electra complex (1913, Jung) in reference to a daughter who feels attraction toward her father and hostility to her mother. Also the name of a daughter of Atlas, and as such a name of one of the Pleiades.
late 14c., "the seven virtues personified;" early 15c., "the Pleiades" (see Pleiades), seven daughters of Atlas and Pleione, placed among the stars by Zeus and popularly known as the Seven Stars (see seven).
In late 20c. applied to seven venerable and prestigious U.S. colleges for women only: Barnard, Bryn Mawr, Mount Holyoke, Radcliffe, Smith, Vassar, and Wellesley. The phrase also was applied to seven similar cannon used by the Scots at Flodden. As a late-20c. name for the major multi-national petroleum companies, Seven Sisters is attested from 1962. They were listed in 1976 as Exxon, Mobil, Gulf, Standard Oil of California, Texaco, British Petroleum, and Royal Dutch Shell.
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.