Origin: before 1000; Middle English; Old English Frīgedæg Freya's day, equivalent to Frīge (genitive singular of Frēo) + dæg day; Frēo is identical with Old English adj. frēo free
O.E. frigedæg "Frigga's day," (see Frigg), Gmc. goddess of married love, a W.Gmc. translation of L. dies Veneris, "day of (the planet) Venus," which itself translated Gk. Aphrodites hemera. Cf. O.N. frijadagr, O.Fris. frigendei, M.Du. vridach, Du. vrijdag, Ger. Freitag
"Friday," and the L.-derived cognates O.Fr. vendresdi, Fr. vendredi, Sp. viernes. In the Gmc. pantheon, Freya (q.v.) corresponds more closely in character to Venus than Frigg does, and some early Icelandic writers used Freyjudagr for "Friday."
A native character in Robinson Crusoe, so named because Crusoe found him on a Friday. Friday places himself in service to Crusoe and helps him survive.
Note: Figuratively, a “man Friday” or “girl Friday” is a valued helper.