What's the difference between i.e. and e.g.?
Old English woruld, worold "human existence, the affairs of life," also "the human race, mankind," a word peculiar to Germanic languages (cf. 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 *wer "man" (Old English wer, still in werewolf; see virile) + *ald "age" (see old).
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" (cf. yard), 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" (e.g. Irish domun, Old Church Slavonic duno, related to English deep); the Lithuanian word is pasaulis, from pa- "under" + saule "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 aion. World power in the geopolitical sense first recorded 1900. World-class is attested from 1950, originally of Olympic athletes.