Thursday before Easter, mid-15c., from Middle English maunde "the Last Supper" (c. 1300), also "ceremony of washing the feet of poor persons or inferiors, performed as a religious rite on Maundy Thursday" (early 14c.), from Old French mandé, from Latin mandatum "commandment" (see mandate (n.)); said to be so called in reference to the opening words of the Latin church service for this day, Mandatum novum do vobis "A new commandment I give unto you" (John xiii:34), words supposedly spoken by Jesus to the Apostles after washing their feet at the Last Supper.
"Shrove Tuesday, last day of carnival, day of eating and merrymaking before the fasting season of Lent," 1690s, French, literally "fat Tuesday," from mardi "Tuesday" (12c. in Old French, from Latin Martis diem "day of the planet Mars;" see Tuesday) + gras "fat," from Latin crassus, "thick," which is of unknown origin.
1722, originally nautical, also close-fights, "bulkheads fore and aft for men to stand behind in close engagements to fire on the enemy," it reflects the confusion of close (v.) and close (adj.); "now understood of proximity, but orig. 'closed' space on ship-board where last stand could be made against boarders" [Weekley]. Compare also closed-minded (1880s), a variant of close-minded, as if "shut" rather than "tight," also closed-fisted, occasional variant of close-fisted "stingy."
People are apt to sneeze, in hot weather for example; and people do not die of sneezing now-a-days, as they did in days that no one knows any thing about. We cannot give six draughts a-day, at one and nine pence each, for sneezing: call it the hay-fever. What a wonderful man! what a clever man! he understands the hay-fever: call him in! Thus is the hay-fever among the last in the list of fashionables. ["On Fashions in Physic," London Magazine, October 1825]
1890, from French fin de siècle "end of century," phrase used as an adjective. At the time it meant "modern;" now it means "from the 1890s." "App. first in title of a comedy, Paris fin de siècle, produced at the Gymnase, Feb. 1890" [Weekley]. French siècle "century, age" is from Latin saeculum "age, span of time, generation" (see secular).
No proof is needed of the extreme silliness of the term. Only the brain of a child or of a savage could form the clumsy idea that the century is a kind of living being, born like a beast or a man, passing through all the stages of existence, gradually ageing and declining after blooming childhood, joyous youth, and vigorous maturity, to die with the expiration of the hundredth year, after being afflicted in its last decade with all the infirmities of mournful senility. [Max Nordau, "Degeneration," English translation, 1895]
"the press," by 1824, and especially from 1831, British English. For the other three, see estate. Earlier the term had been applied in various senses that did not stick, including "the mob" (1752), "the lawyers" (1825). The extension to the press is perhaps an outgrowth of the former.
Hence, through the light of letters and the liberty of the press, public opinion has risen to the rank of a fourth estate in our constitution; in times of quiet and order, silent and still, but in the collisions of the different branches of our government, deciding as an umpire with unbounded authority. ["Memoir of James Currie, M.D.," 1831]
[Newspapers] began to assume some degree of political importance, during the civil wars of the seventeenth century, in England; but it is not until within the last fifty years that they have become, — as they are now justly styled, — a Fourth Estate, exercising a more powerful influence on the public affairs of the countries in which they are permitted to circulate freely, than the other three put together. [Alexander H. Everett, "Address to the Phi Beta Kappa Society of Bowdoin College," 1834]
parting salutation, 1860, of unknown origin, perhaps from a German idiom (compare German parting salutation adieu so lange, the full sense of which probably is something like "farewell, whilst (we're apart)"); or perhaps from Hebrew shalom (via Yiddish sholom). Some have noted a similarity to Scandinavian leave-taking phrases, such as Norwegian Adjø så lenge, Farvel så lenge, Mor'n så lenge, literally "bye so long, farewell so long, morning so long;" and Swedish Hej så länge "good-bye for now," with så länge "for now" attested since 1850 according to Swedish sources. Most etymology sources seem to lean toward the German origin. So long (adv.) "for such a long time" is from late Old English.
Earlier guesses that it was a sailors' corruption of a South Pacific form of Arabic salaam are not now regarded as convincing. "Dictionary of American Slang" also adds to the list of candidates Irish slán "safe," said to be used as a salutation in parting. The phrase seems to have turned up simultaneously in America, Britain, and perhaps Canada, originally among lower classes. First attested use is in title and text of the last poem in Whitman's "Leaves of Grass" in the 1860 edition.
An unknown sphere, more real than I dream'd, more direct, darts awakening rays about me — So long!
Remember my words — I may again return,
I love you — I depart from materials;
I am as one disembodied, triumphant, dead.
Whitman's friend and fan William Sloane Kennedy wrote in 1923:
The salutation of parting — 'So long!' — was, I believe, until recent years, unintelligible to the majority of persons in America, especially in the interior, and to members of the middle and professional classes. I had never heard of it until I read it in Leaves of Grass, but since then have quite often heard it used by the laboring class and other classes in New England cities. Walt wrote to me, defining 'so long' thus: "A salutation of departure, greatly used among sailors, sports, & prostitutes — the sense of it is 'Till we meet again,' — conveying an inference that somehow they will doubtless so meet, sooner or later." ... It is evidently about equivalent to our 'See you later.' The phrase is reported as used by farm laborers near Banff, Scotland. In Canada it is frequently heard; 'and its use is not entirely confined to the vulgar.' It is in common use among the working classes of Liverpool and among sailors at Newcastle-upon-Tyne, and in Dorsetshire. ... The London Globe suggests that the expression is derived from the Norwegian 'Saa laenge,' a common form of 'farewell,' au revoir. If so, the phrase was picked up from the Norwegians in America, where 'So long' first was heard. The expression is now (1923) often used by the literary and artistic classes.