Middle English sabat, from Old English sabat "seventh day of the week in the Jewish calendar; Saturday" as observed by the Jews as a day of rest from secular employment and of religious observance, from Old French sabat and directly from Latin sabbatum, from Greek sabbaton, from Hebrew shabbath, properly "day of rest," from shabath "he rested" (from labor). The spelling with -th is attested from late 14c. but was not widespread until 16c.

The Babylonians regarded seventh days as unlucky, and avoided certain activities on them; the Jewish observance might have begun as a similar custom. Among European Christians, the time of "Sabbath" shifted from the seventh day to the first (Sunday) via the Christians' celebration of the Lord's resurrection on the first day of the week (a Christian Sabbath) "though no definite law, either divine or ecclesiastical, directed the change" [Century Dictionary], but elaborate justifications have been made. In English Sabbath as "Sunday" is evident by early 15c. The sense change was completed among the English people generally during the Reformation.

The original use of the word is preserved in Spanish Sabado, Italian Sabato, and other languages' names for "Saturday." Hungarian szombat, Rumanian simbata, French samedi, German Samstag "Saturday" are from Vulgar Latin *sambatum, from Greek *sambaton, a vulgar nasalized variant of sabbaton. Gothic Sabbato, Sabbatus probably are directly from Greek.

The meaning "any day (or month or year) in which religious rest is enjoined" is by late 14c.; the word also was used in Medieval Latin of any feast day, the solstice, etc. Sabbath-breaking "act of profaning the Sabbath" is attested from 1650s (to break the Sabbath is from late 14c.), formerly a legal violation in parts of the old U.S., "immoral, disturbing, or unnecessary labors or practices" [Century Dictionary]. Sabbath-school is by 1798.

"witches' sabbath," a midnight meeting supposed to have been held annually by demons, sorcerers, and witches under the leadership of Satan, to celebrate their orgies, 1650s, a special application of the French form of Sabbath (q.v.).

"pertaining to the Sabbath or its observance," 1630s, from Latin sabbatarius (adj.), from sabbatum (see Sabbath).

1934, from Hebrew shabbat (see Sabbath). Earlier in English as Shabbos (1870), from Yiddish shabes. Hence the salutation Shabbat shalom "a peaceful sabbath."

"armies, hosts," only in Scripture, "the heavenly hosts," used as part of a title of God (Lord of Sabaoth), early 14c., from Late Latin Sabaoth (pl.), from Greek Sabaoth, transliterating Hebrew tzebhaoth "hosts, armies," plural of tzabha "army," from tzaba "he waged war, he served."

The word was translated in English in the Old Testament by the phrase "Lord of Hosts," but left untranslated in the New Testament (and in the "Te Deum") in Lord of Sabaoth. It sometimes is confused with unrelated Sabbath.

1590s, "recurring in sevens or on every seventh;" 1640s, "of or suitable for the Sabbath," from Latin sabbaticus, from Greek sabbatikos "of the Sabbath," from sabbaton (see Sabbath). By 1836 as "characterized by rest or cessation from labor or tillage." Other adjectives from Sabbath include Sabbatary, Sabbatine.

 The noun meaning "a year's absence granted to researchers" (originally one year in seven, to university professors) is from 1934, short for sabbatical year, etc., which was recorded by 1886 (the thing itself is attested from 1880, at Harvard), a term perhaps suggested by the sabbatical year (1590s) in Mosaic law, the seventh year, in which land was to remain untilled and non-foreign debtors and slaves released.

also sometimes Sabbatharian, 1610s, "a Christian or Jew unusually strict about Sabbath observation," from Latin sabbatarius (adj.), from sabbatum (see Sabbath). Especially of members of Christian sects which maintained the Sabbath should be observed on the seventh day of the week (and not the first) is from 1640s; earlier sabbatary (1590s). It took on tones of reproach when used of Puritans deemed overzealous to interdict worldly pastimes and recreations on the Sabbath.

Not to be confused with Sabbatian (n.) "member of a sect founded by Sabbatus, a convert from Judaism "who seceded from the Novatianists before 380, having adopted Quartodeciman views" [OED]. Related: Sabbatartianism. Sabbatism is used in the general sense of "observance of the Sabbath or a sabbath as a day of rest from labor" (from Late Latin sabbatismus, from Greek sabbatismos).

seventh or last 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 hēmera, literally "the day of Cronus."

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

Unlike other English day names there was no Germanic substitution, perhaps because the northern European pantheon lacks a match to Roman Saturn. A homely ancient Nordic custom seems to be preserved in Old Norse day names laugardagr, Danish lørdag, Swedish lördag "Saturday," literally "bath day" (Old Norse laug "bath").

Saturday night has been figurative of revelry and especially "drunkenness and  looseness in relations between the young men and young women" ["Clara Hopwood"] at least since 1847. Saturday-night special "cheap, low-caliber handgun" is American English, attested from 1976 (earlier Saturday-night pistol, 1929).

capital of Tajikistan, from Tajik dushanbe "Monday" (a compound of du "two" + Shanbe "Saturday," literally "Sabbath;" thus "two days after Saturday"); so called in reference to a regular Monday market there. Known from 1929-1961 as Stalinabad.

late 14c., "laborious, subordinate, appropriate to a servant or to the class of slaves," originally in reference to work that it is forbidden to do on the Sabbath, from Latin servilis "of a slave" (as in Servile Wars, name given to the slave revolts in the late Roman Republic), also "slavish, servile," from servus "slave" (see serve (v.)). Related: Servilely.

By mid-15c. as "of the rank of a servant; of or pertaining to servants;" the sense of "cringing, fawning, mean-spirited, lacking independence" is recorded from c. 1600 The earliest sense in English was Church-legal, servile work being forbidden on the Sabbath. The phrase translates Latin opus servilis, itself a literal translation of the Hebrew words.