[The Squatter of Amon Rûdh]

Although the only usable definition of this word is the one invented by Tolkien, it does occur in the Denham Tracts, a series of jottings on folklore collected by Michael Denham during the 1840s and 50s. It appears in a list of supernatural creatures, and is defined by Denham as 'a class of spirit'. There's an outside possibility that Tolkien had read this work and remembered the name, but it's more likely to be a coincidence.

This information came to light in 1979, but the staff of the Oxford English Dictionary had previously asked Tolkien for a definition of 'Hobbit', which still forms the basis for theirs.