SaturdayyoudaoicibaDictYouDict[Saturday 词源字典]
Saturday: [OE] Saturday is etymologically ‘Saturn’s day’. Old English Sæterdæg was short for Sæternes dæg, a translation of Latin Sāturnī diēs ‘Saturn’s day’. Saturn [OE] itself, as the name of both the god and the planet, comes from Latin Sāturnus, which may have been of Etruscan origin. In ancient Rome, the festival held in honour of Saturn, which took place in December, was the occasion for fairly uninhibited revelry.

It was called the Sāturnālia, which English acquired as saturnalia [16]. Those born under Saturn, by contrast, were considered by ancient and medieval astrologers to be of gloomy temperament – hence the adjective saturnine [15].
=> saturn, saturnalia, saturnine[Saturday etymology, Saturday origin, 英语词源]
Saturday (n.)youdaoicibaDictYouDict
seventh day of the week, Old English sæterdæg, sæternesdæg, literally "day of the planet Saturn," from Sæternes (genitive of Sætern; see Saturn) + Old English dæg (see day). Partial loan-translation of Latin Saturni dies "Saturn's day" (compare Dutch Zaterdag, Old Frisian Saterdi, Middle Low German Satersdach; Irish dia Sathuirn, Welsh dydd Sadwrn). The Latin word itself is a loan-translation of Greek kronou hemera, literally "the day of Cronus."

Unlike other English day names, no god substitution seems to have been attempted, perhaps because the northern European pantheon lacks a clear corresponding figure to Roman Saturn. A homely ancient Nordic custom, however, seems to be preserved in Old Norse laugardagr, Danish lørdag, Swedish lördag "Saturday," literally "bath day" (Old Norse laug "bath").

German Samstag (Old High German sambaztag) appears to be from a Greek *sambaton, a nasalized colloquial form of sabbaton "sabbath," also attested in Old Church Slavonic sabota, Polish sobota, Russian subbota, Hungarian szombat, French samedi.

Saturday night has been used figuratively to suggest "drunkenness and looseness in relations between the young men and young women" since at least mid-19c. Saturday-night special "cheap, low-caliber handgun" is American English, attested from 1976 (earlier Saturday-night pistol, 1929).