In that century, the term "prescheme" had a certain cachet in mathematics. It wouldn't surprise me if the name choice for this scheme dialect was in part a nod to the math term:
>In the early days, this was called a prescheme, and a scheme was defined to be a separated prescheme. The term prescheme has fallen out of use, but can still be found in older books, such as Grothendieck's "Éléments de géométrie algébrique" and Mumford's "Red Book".
For a while now I've toyed with the idea of trying to build a Racket-like ecosystem on top of Pre-Scheme. I like the "language playground" experience of Racket, but one thing that holds me back from playing with it more is that it's tied to a fairly heavyweight run-time. That makes it a bit more difficult to take it some of the places I'd like to go with it.
Kelsey's paper is from 01997 but I think Pre-Scheme itself is from about 01993? Squeak came out in 01996 but I think had been in development for a year or two. The Squeak paper also came out in 01997.
The earliest concrete evidence for pre-scheme I can find is that version 0.52 of Scheme 48 (1998) has a prescheme directory [1]. It lists a handful of releases going back as far as 1986, though who knows at what point pre scheme was introduced.
I remember when the Squeak paper came out I had the reaction, "Oh, kind of like Pre-Scheme, why doesn't this mention it?" (Maybe unfair: nobody can keep up with everything, and I can't remember if Pre-Scheme had been documented at all.)
https://en.wikipedia.org/wiki/Scheme_(mathematics)
>In the early days, this was called a prescheme, and a scheme was defined to be a separated prescheme. The term prescheme has fallen out of use, but can still be found in older books, such as Grothendieck's "Éléments de géométrie algébrique" and Mumford's "Red Book".