Old English woruld, worold "human existence, the affairs of life," also "a long period of time," also "the human race, mankind, humanity," a word peculiar to Germanic languages (cognates: Old Saxon werold, Old Frisian warld, Dutch wereld, Old Norse verold, Old High German weralt, German Welt), with a literal sense of "age of man," from Proto-Germanic *weraldi-, a compound of *wer "man" (Old English wer, still in werewolf; see virile) + *ald "age" (from PIE root *al- (2) "to grow, nourish").
Originally "life on earth, this world (as opposed to the afterlife)," sense extended to "the known world," then to "the physical world in the broadest sense, the universe" (c. 1200). In Old English gospels, the commonest word for "the physical world," was Middangeard (Old Norse Midgard), literally "the middle enclosure" (see yard (n.1)), which is rooted in Germanic cosmology. Greek kosmos in its ecclesiastical sense of "world of people" sometimes was rendered in Gothic as manaseþs, literally "seed of man." The usual Old Norse word was heimr, literally "abode" (see home). Words for "world" in some other Indo-European languages derive from the root for "bottom, foundation" (such as Irish domun, Old Church Slavonic duno, related to English deep); the Lithuanian word is pasaulis, from pa- "under" + saulė "sun."
Original sense in world without end, translating Latin saecula saeculorum, and in worldly. Latin saeculum can mean both "age" and "world," as can Greek aiōn. Meaning "a great quantity or number" is from 1580s. Out of this world "surpassing, marvelous" is from 1928; earlier it meant "dead." World Cup is by 1951; U.S. baseball World Series is by 1893 (originally often World's Series). World power in the geopolitical sense first recorded 1900. World-class is attested from 1950, originally of Olympic athletes.
1712, "belonging to a prehistoric age," see old + world. Meaning "of or pertaining to Eurasia and Africa," as opposed to the Americas, is by 1877. The noun phrase Old World in this sense is by 1590s. The division of the earth into Old World and New World among Europeans dates to 1503 and Italian explorer Amerigo Vespucci's use of Latin Mundus Novus for the lands of the western hemisphere found by Columbus and others, indicating they were not part of Asia.
The Known World is usually divided into four Parts, Europe, Asia, Africk and America. But it is a most unequal Division, and I think it more rational to divide it thus. Viz. the Known World, first into two Parts, the Old and the New World; then the Old World into three, Europe, Asia, and Africa; and the New into two, the Northern and Southern America. [Guy Miege, "A New Cosmography, or Survey of the Whole World," London, 1682]
attested by 1898 as a speculation.
If through fear of entangling alliances the United States should return the Philippines to Spain, Mr. Page asserted that the predatory nations would swoop down upon them and a world war would result. [New York Times, Dec. 16, 1898]
Applied to the first one almost as soon as it began in 1914 ("England has Thrown Lot with France in World War" — headline, Pittsburgh Press, Aug. 2, 1914). World War I was coined 1939, replacing Great War as the most common name for it; First World War, World War II, and Second World War all also are from 1939. Old English had woruldgewinn, woruldgefeoht, both of which might be translated "world war," but with "world" in the sense of "earthly, secular."