Outside of D&D, whenever anyone thinks of a gnome, they are more likely to think of a "garden gnome" or (something along the lines of "David the Gnome"), not how they are presented in D&D.
There's plenty of information out there about gnomes in-universe, but out of universe, why are they as they are and not more like garden gnomes (i.e. Tiny Fey creatures, most likely)? What influences inspired the D&D gnome as it first appeared, and continues to appear today?
This came up because I was recently getting a couple of people into D&D using the 5e starters set, but I also brought the PHB along to allow for all races and classes (since I wanted them to have more variety whilst creating characters). I was describing each to them, and all the other races made sense to them, but then we got to gnomes.
What they imagined were garden gnomes, whereas what I was describing sounded more like an alternative to a halfling. The best way I could describe it in the end is basically like a more magically-inclined halfling; "they are to halflings what elves are to humans", which they accepted (in a "if you say so…" kind of way) but it still brought to my attention how weird it is that gnomes are what they are in D&D.
So, how come gnomes in D&D are as they are and not more like garden gnomes or another more common depiction of gnomes?
Note: I am not asking about wanting to change them in any way, since I like D&D gnomes as they are, but it doesn't make much sense to me as to why they are like that to begin with. This also isn't about why they're not considered Tiny in 5e since all playable races are Small or Medium in 5e.
I am definitely not asking for designer-reasons that can only be answered with Crawford tweets or whatever, nor anything from Gary Gygax back in the day (although these sorts of quote won't be rejected either; they're just not mandatory), simply what other depictions of gnomes exist that differ from the garden gnome that may have influenced how they currently are in D&D.
This isn't about any system in particular, hence why this isn't tagged dnd-5e but rather dungeons-and-dragons, since as far as I can tell, they've always kinda been as they are presented in 5e throughout all editions, although I only really know about 3.5e (via NWN2) and 5e.
Best Answer
As far as I can tell, the D&D Gnomes are somewhat of a hybrid between Gnomes and Nisse (the "inspiration" for Garden Gnomes)
D&D actually has a surprising level of research and ancient, somewhat-obscure mythologies behind it, as can be seen from the Gorgon in this answer.
The earliest forms of gnomes called as-such (well, technically they were called "genomos", but it's close) are thought to date from the 16th century, featuring in Ex Libro de Nymphis, Sylvanis, Pygmaeis, Salamandris et Gigantibus, by the Swiss scholar Paracelsus. They are a form of Earth Elemental that manifests as a small, human-like figure, about two "spans" (one cubit) tall, and can move through solid earth like it was air.[2]
Gnomes really became popular during the 18th Century in fairy tales, where they were typically depicted as the benevolent and ingenious guardians of treasures and mines. Nicolas-Pierre-Henri de Montfaucon de Villars, the Abbot of the town of Villars, France, and who was the source for Alexander Pope's The Rape of the Lock, describes gnomes in this way[3]:
This is likely where the D&D source for gnomes comes from: inventive, benevolent creatures who enjoy gems ("Precious Stones") as well as their procurement.
Meanwhile, it is also interesting to note that Garden Gnomes are derived from the Scandinavian Nisse/Tomte/Tomtenisse, which is an ancestral farming spirit which ranges from a few inches to half the height of a human (or almost analogous to their size in D&D, 3-4 feet high), but the Nisse itself is more like a winter version of a Gnome than what a Garden Gnome is.
Overall, I suspect that the D&D version of Gnomes combines several aspects of gnomes from history into one type of creature.
This was actually a fun question to research for, thank you.
(1 is in-use by the link for Gorgons)
[2]Lewis, C. S. (1964). The Discarded Image - An Introduction to Medieval and Renaissance Literature. Cambridge University Press. p. 135. ISBN 0-521-47735-2.
[3] Montfaucon de Villars, Nicolas-Pierre-Henri (1680). The Count of Gabalis: Or, The Extravagant Mysteries of the Cabalists, Exposed in Five Pleasant Discourses on the Secret Sciences. Translated by Gent, P. A. London: B. M. Printer. pp. 29–30. OCLC 992499594.