Earlier quoted context omitted.
> The o.g. iPad Air we bought in Nov 2020 o.g. ?
It's kid slang for "original", apparently.
I started using "OG" ~16 years ago to disambiguate the Motorola Droid that I had (which was the first Android phone available from Verizon) from the Droid 2, 3, and 4 that came later.
"OG Motorola Droid" has specificity, while "Motorola Droid 1" is something that never existed.
Anyway, my usage is old enough to drive a car. :)