first day of the week, Old English sunnandæg (Northumbrian sunnadæg), literally "day of the sun," from sunnan, oblique case of sunne "sun" (see sun (n.)) + dæg "day" (see day). A Germanic loan-translation of Latin dies solis "day of the sun," which is itself a loan-translation of Greek hēmera heliou. Compare Old Saxon sunnun dag, Old Frisian sunnandei, Old Norse sunnundagr, Dutch zondag, German Sonntag "Sunday."
In European Christian cultures outside Germanic often with a name meaning "the Lord's Day" (Latin Dominica). Sunday-school dates from 1783 (originally for secular instruction); Sunday clothes is from 1640s. Sunday driver is from 1925.
*sāwel-, Proto-Indo-European root meaning "the sun." According to Watkins, the *-el- in it originally was a suffix, and there was an alternative form *s(u)wen-, with suffix *-en-, hence the two forms represented by Latin sol, English sun.
It forms all or part of: anthelion; aphelion; girasole; heliacal; helio-; heliotrope; helium; insolate; insolation; parasol; parhelion; perihelion; Sol; solar; solarium; solstice; south; southern; sun; Sunday.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit suryah, Avestan hvar "sun, light, heavens;" Greek hēlios; Latin sol "the sun, sunlight;" Lithuanian saulė, Old Church Slavonic slunice; Gothic sauil, Old English sol "sun;" Old English swegl "sky, heavens, the sun;" Welsh haul, Old Cornish heuul, Breton heol "sun;" Old Irish suil "eye;" Avestan xueng "sun;" Old Irish fur-sunnud "lighting up;" Old English sunne German Sonne, Gothic sunno "the sun."
1550s, "of or pertaining to Christ as Lord;" 1620s, "of or pertaining to Sunday (as the Lord's day)," from Medieval Latin dominicalis, "pertaining to Sunday; pertaining to the Lord," from Latin dominicus, from dominus "lord," from domus "house" (from PIE root *dem- "house, household").
"Low Sunday," 1706, Quasimodo Sunday, from Latin quasi modo, first words of introit for the first Sunday after Easter: quasi modo geniti infantes "as newborn babes" (1 Peter ii.2). The hunchback in Hugo's novel was abandoned as an infant at Notre Dame on this day, hence his name. For first element, see quasi; for second, see mode (n.1).
legal Latin phrase meaning "day in which courts are not held" (Sunday, etc.), short for dies non juridicus "not a court day."
"motherly care," 1868, verbal noun from mother (v.). Earlier it was used in reference to the rural custom of visiting one's parents with presents on Mid-Lent Sunday (1640s).