Today happens to be my brother’s birthday. But not just any birthday. His fortieth birthday. And as someone who was constantly teased while I was little, let’s just say I’m enjoying this a lot. So let’s look at things relating to age, shall we?
Age first showed up in the late thirteenth century as a noun, and then in the late fourteenth century as a verb—although initially it only referred to an era of time, before also referring to how old someone was. It comes from the Old French aage/eage/edage, age or lifetime, from the Vulgar Latin aetaticum. That’s from the classical Latin aetatem, age, from aevum, age (like, a slightly different form of age). It can be traced all the way back to the Proto Indo European aiw-, vital force or life.
Old comes from the Old English ald/eald, old. It comes from the Proto Germanic althaz, adult, which is related to the Proto Indo European root al-, meaning grow or nourish. Also related are the words elder and eldest, which once upon a time used to be what we used when we wanted to say older and oldest. There’s also a tree called an elder, but that one isn’t related at all.
Senior showed up in the late thirteenth century from the classical Latin senior, which just means older. No real surprises in this one. But it is from the word senex (old man) and can be traced to the Proto Indo European sen-, old, which is the origin word for words like sir and senor, which is pretty neat.
Lastly today, we’ll look at ancient. It showed up in the late fourteenth century as auncyen, which meant very old people before also meaning very old things. It’s from the Old French ancient, old or ancient, and the Vulgar Latin anteanus. Now, that word is taken from the classical Latin ante, which I’m sure you all recognize and also means before. It’s related to the Proto Indo European ant-, which means front or fore [https://www.etymonline.com/word/*ant-], but I can’t quite see how we derived old from that.
Tony Jebson’s page on the Origins of Old English