For those who don't read Spanish (and my own Junior High/High School Spanish has atrophied to an alarming extent), here's the gist:
We know that the word HOBBIT appears in Denham's list from the 1850s, but we don't know where Denham got the word. It's not in Reginald Scot's THE DISCOVERIE OF WITCHCRAFT , his primary source. Of the five texts we have of Denham's list, only the last two include the word "hobbit" (one of these being in the collection THE DENHAM TRACTS, published long after Denham's death).
We also don't know if Tolkien was aware of Denham's list. It's my own belief that Tolkien made up the word independently, but it's a debatable point. In any case, finding out where Denham got it would be a real breakthrough.
And that's just what it looks like Diego might have done. Starting from my discussion of Mr. Denham's Hobbit in Appendix I to RETURN TO BAG END, he noted that Denham cites Capn. Francis Grose as his source on a particular point. Following up on this, Diego has tracked down Grose's 1787 book A PROVINCIAL GLOSSARY, WITH A COLLECTION OF LOCAL PROVERBS AND POPULAR SUPERSTITIONS, which I was totally unaware of, and found therein several of the names absent from Scot but appearing in Denham, making it v. likely that Grose is Denham's source for these creatures. Among them are a number of Northern folk-lore creatures (i.e., so identified as Northern by Grose), like the bar-guest, boggart, boggle, dobby, fetch, swarth, and most importantly hobbil, hobgobbin, hobgoblin, and hobthrust/hob o t'hurst.
Grose glosses both HOBBIL and HOBGOBBIN as "a natural fool, a blockhead".
By contrast, he defines HOBGOBLIN as "an apparition, fairy, or spirit"
HOBTHRUST, which like Denham he believes properly breaks down as HOB O T'HURST, is "a spirit, supposed to haunt woods only".
In addition, he also gives HOB/HUB ("the back of the chimney: to make a hob, to make a false step; probably hence to hobble"), HOB-NOB ("at a venture, rashly"), and HOBBETY-HOY ("neither man nor boy, a young man between both").
So, while 'hobgoblin' and 'hobthrust' are much as in Denham, with 'Hob' equaling Lob or Brownie, Grose's two new variations 'hobbil' and 'hobgobbin' both seem to belong to the 'Hob' = 'rustic simpleton' tradition.
The most intriguing thing about this though is that, since Denham's various lists do have some typos, this opens up the possibility that HOBBIT in his 1853 list might well be an accidental mis-spelling of HOBBIL. If so, then Diego has in all probability found Denham's direct source. Even if not, the combination of HOBBIL and HOBBETY (in Hobbity-hoy) is suggestive.
Points for future research (some of which I hope to carry out later this week -- if so, I'll do an update):
(1) the text Diego used is from the 1811 reprinting of Grose's book, this being the verison available on Google Books
--how is the word spell in the orignal 1787 edition? (Suzzallo-Allen has a microfilm, so that point shd be easy to resolve).
(2) Did Haigh or Wright cite Grose in their respective works? If so, this wd increase the chances that Tolkien was aware of Grose's book. (I believe Suzzallo-Allen has Wright but not I don't have access to a copy of the Haigh)
So, the search goes on, but Diego has opened up a new avenue of inquiry, which tends to confirm the rustic, hob/lob, and Northern associations of our missing hob(bit). Well done!