Via https://en.wikipedia.org/wiki/PEEK_and_POKE:
> One of the earliest references to these commands in BASIC, if not the earliest, is in Altair BASIC[4].
[4] https://archive.org/stream/bitsavers_mitsMITSAl_6669937/MITS...
So, it seems to date back to 1975.
POKE
(who named these interesting commands?)