Looking at old PC keyboards, from IBM Model M to old Gateway 2000 keyboards from the 90's etc, it's looks like it's always been Enter.

But terminals and UNIX machines were more likely to use "Return", e.g. looking at a DEC VT100 or Sun SPARCstation keyboard.

edit: looks like most of the 8-bit machines like Commodore, Atari also used Return. So Enter was mostly an IBM thing.

The original IBM PC keyboard just used an arrow. The keyboard that shipped with the PC AT used Enter, while the enhanced keyboard (Model M) used an arrow for ISO layout keyboards, Enter for ANSI keyboards, and I think some variants for non-PC platforms used Field Exit, which was also used by IBM for many keyboards before the PC. I'm not sure what other vendors may have used, I'm sure there are some return keys out there, and for all I know IBM did ship keyboards with Return instead of Enter.

The word "enter" has now lost all meaning in my brain, but it does look a little weird on my keyboard. Never paid much attention in my 25+ years of computing.