old: [OE] Etymologically, old means ‘grown-up’. It comes from a prehistoric West Germanic *altha (source also of German alt and Dutch oud) which was a past-participial adjective formed from the base of a verb meaning ‘grow, nourish’. (A precisely similar formation from the related Latin verb adolēscere ‘grow’ has given English adult, and Latin altus ‘high’ – source of English altitude [14] – was originally a past-participial adjective too, derived from alēre ‘nourish’, although it has metaphoricized ‘growing’ to ‘height’ rather than ‘age’.) Elderly and the comparative and superlative elder, eldest come ultimately from the same source. World began life as a compound noun of which the noun *ald- ‘age’, a relative of old, formed the second element. => adult, altitude, elder, world
old (adj.)
Old English ald (Anglian), eald (West Saxon) "aged, antique, primeval; elder, experienced," from Proto-Germanic *althaz "grown up, adult" (cognates: Old Frisian ald, Gothic alþeis, Dutch oud, German alt), originally a past participle stem of a verb meaning "grow, nourish" (compare Gothic alan "to grow up," Old Norse ala "to nourish"), from PIE root *al- (3) "to grow, nourish" (cognates: Greek aldaino "make grow, strengthen," althein, althainein "to get well;" Latin alere "to feed, nourish, bring up, increase," altus "high," literally "grown tall," almus "nurturing, nourishing," alumnus "fosterling, step-child;" Old Irish alim "I nourish").
The usual PIE root is *sen- (see senior (adj.)). A few Indo-European languages distinguish words for "old" (vs. young) from words for "old" (vs. new), and some have separate words for aged persons as opposed to old things. Latin senex was used of aged living things, mostly persons, while vetus (literally "having many years") was used of inanimate things. Greek geraios was used mostly of humans; Greek palaios was used mostly of things, of persons only in a derogatory sense. Greek also had arkhaios, literally "belonging to the beginning," which parallels French ancien, used mostly with reference to things "of former times."
Old English also had fyrn "ancient," related to Old English feor "far, distant" (see far, and compare Gothic fairneis, Old Norse forn "old, of old, of former times," Old High German firni "old, experienced"). The original Old English vowel is preserved in Scots auld, also in alderman. The original comparative and superlative (elder, eldest) are retained in particular uses.
First record of old-timer is from 1860. Expression old as the hills first recorded 1819. The good old days dates from 1828. Of old "of old times" is from late 14c. Old maid "woman who remains single well beyond the usual marrying age" is from 1520s; the card game is attested by that name from 1844. Old man "man who has lived long" is from c. 1200; sense of "husband, father, boss" is from 1854, earlier (1830) it was military slang for "commanding officer;" old lady "wife, mother" is attested from c. 1775. Old English is attested from 1701, originally as a type of font. Old boy originally was a former pupil of one of the English public schools. Old Testament attested from mid-14c.