I usually write about words that are hard to find, and sometimes about words that are interesting in some unusual way. But I hardly ever mention words that don’t exist at all. But as you might guess — well, OK, maybe you wouldn’t guess because why would you even be thinking about it — regardless, there’s a word for words that aren’t words.
The oldest record of it found by the OED comes from 1637: “A judicious and learned Mathematician, as you seem to be, would have considered with Xylander, that διοπτικὰ, is vox nihili, no word at all, a mistake meerly of the transcripts.” “Vox nihili”, which is the word (or phrase, as the case may be) for a non-word, is borrowed from Latin. A straight translation makes it “voice nothing.”
In spite of the vast opportunities English offers to get obscure words wrong, or just make something up and assume nobody’s going to notice, “vox nihili” is not used very much at all. It seem to mostly be inserted into relatively academic writing, but in 1884 the Saturday Review printed it for just anybody to read: “Now and again, a mere vox nihili of earlier dictionary-makers..has been run down to its original error and exploded.”
It’s still used here and there. As recently as 2015 it showed up in Mantissa: “The Coislinianus offers ‘Gaiatianus’, a name which does not and could not exist. The manuscripts of Photius offer ‘Gaitianus’, another vox nihili.” You might not have run across Mantissa before; it’s a book by Jonathan Barnes, who is a professor of classic philosophy at Oxford. His other best sellers (maybe soon to appear as Netflix originals) include Aristotle’s Posterior Analytics, The Toils of Skepticism, and Porphyry: Introduction. But you might possibly have heard of or read novels by Julian Barnes. They’re brothers. And by the way, if you’re wondering about that last title, he’s not talking about porphyry the kind of rock; there was a Greek philosopher named Porphyry back in the third century.