SundayyoudaoicibaDictYouDict[Sunday 词源字典]
Sunday: [OE] Sunday is part of the general system of naming days of the week after heavenly bodies inherited by the Germanic peoples from the ancient Mediterranean world. The Romans called the day diēs sōlis ‘day of the sun’, which in translation has become German sonntag, Dutch zondag, Swedish söndag, Danish söndag, and English sunday. Welsh retains the term (dydd sul), but the Romance languages have gone over to variations on ‘Lord’s day’ (French dimanche, Spanish domingo, etc).
[Sunday etymology, Sunday origin, 英语词源]
Sunday (n.)youdaoicibaDictYouDict
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 hemera 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.