There is no official terminology for non-spellcasters other than "non-spellcasters."
From the DMG Errata (P.1):
About Attunement (PHB 136)
The first paragraph ends with a new sentence:
“If the prerequisite is to be a spellcaster, a creature qualifies if it can cast at least one spell using its traits or features, not using a magic item or the like.”
For the purpose of attunement:
If a creature is able to cast a spell by virtue of their own ability (not from an item), whether that be race, class, or feature, they are a spellcaster.
If a creature isn't able to cast a spell by virtue of their own ability (not from an item), whether that be race, class, or feature, they aren't a spellcaster.
The books until Eberron: Rising from the Last War offers no further terminology about non-spellcasters that goes beyond "creature" which also applies to spellcasters, so for the purpose of the restriction and clarity I recommend the term "non-spellcaster" which are defined as lacking all the qualities a spellcaster has without introducing any lingo.
I have done so while homebrewing magic-items and my table understood what non-spellcasters were after I told them how they are distinct from spellcasters.
In Eberron: Rising from the Last War non-spellcasters are mentioned exactly once on the table for Library Vault Adventures (ERftLW 226)
Destroy a scroll containing an incantation that allows even non-spellcasters to animate the dead.
There is no consistent use of that language elsewhere.