Normally not - I tihnk. I can see it as a granted spell from a deity, or as a homebrew - but both of these concepts exisited at that time.

But it was not commonly used to refer to spontaneous casters with an innate skill for magic.

Not until we got the WoTC trio of books in 2000.

So... "The Duffer Brothers"... care to explain how your child characters are SO GOOD at D&D, they're playing an unreleased version 13 years early? HMMMM?

The term "sorcerer" was used in pre 3rd Ed D&D, but mostly as a generic term for arcane spellcaster - the same way one might use "mage" or "magic-user". It was, in some instances, used to refer to very high level wizards as an informal rank or title.

Why am I like this?

Oh jesus

I have read this as a challenge for future events.