'Old' literally means 'grown up' — past participle of PIE *h2el- (to grow), kin to Latin 'altus' (high).
Having lived for a long time; no longer young; belonging to the past, former.
From Old English 'eald' (also 'ald'), from Proto-Germanic *aldaz, the past participle of *alan meaning 'to grow, to nourish.' The PIE root is *h₂el- meaning 'to grow, to nourish.' The original sense was literally 'grown up' — age conceived as the result of having