Tolkien actually addressed this himself.
“Nomenclature of
the Lord of the Rings” was an essay written by Tolkien for translators. It was photocopied by Allen & Unwin, his publishers, and shared for many years. It first appeared in print in
A Tolkien Compass by Christopher Tolkien in 1975; this is from an appendix to
Reader’s Companion.
─◊─
Orc. This is supposed to be the CS name of those
creatures at that time. It should therefore according to the system be translated into E. or the LT. It was translated ‘
goblin’ in
The H., except in one place; but this word, and other words of similar sense in other European
languages (as far as I know), are not really suitable. The
orc in
The L.R. and
The Silmarillion, though of course partly made out of traditional features, is not really comparable in supposed origin, functions, and relation to the
Elves. In any case
orc seemed to me, and seems, in sound a good name for these creatures. It should be retained.
It should be spelt
ork (so in the Dutch translation) in a Germanic LT, but I had used the spelling
orc in so many
places that I have hesitated to change it in the E. text, though the adjective is necessarily spelled
orkish. (The Grey-elven form is
orch, pl.
yrch.
(I originally took the word from OE
orc (
Beowulf 112,
orc-neas and the gloss
orc =
Þyrs ‘ogre’,
heldeofol ‘hell-devil’). This is supposed not to be connected with the modern E.
orc,
ork, a name applied to various sea-beasts of the dolphin-order.)
─◊─
Paragraph two has an unclosed parenthesis, which I have reproduced. “CS” is “
Common Speech”, “E.” is “English”, “LT” is the “language used in translation”, “OE” is “Old English” (Anglo-Saxon).
I will dare to disagree a bit with Galin concerning
uruk – a dangerous thing to do, since his grasp of Tolkien’s languages far exceeds mine. But Appendix F says of
uruk,
─◊─
Orcs and the Black Speech. Orc is the form of the name that
other races had for this foul people… In
Sindarin it was
orch. Related, no doubt, was the word
uruk of the Black Speech, though this was applied as a rule only to the great soldier-orcs that at this time issued from
Mordor and
Isengard. The lesser kinds were called, especially by the
Uruk-hai,
snaga ‘slave’.
─◊─
And at the end of the section on Orcs, he writes
─◊─
But at the end of
the Third Age a troll-race not before seen appeared…
Olog-hai they were called in the Black Speech. … a fell
race, strong, agile, fierce and cunning, but harder than stone. Unlike the older
races of the Twilight they could endure the sun…
─◊─
I deduce from this that the suffix
-hai means “great”, so that
uruk-hai is “
great orcs” and
olog-hai “great
trolls”.
And just to stir controversy, I think these olog-hai were
half-trolls bred from
Entwives: their physical description as “clad only in close-fitting mesh of horny scales, or maybe that was their hideous hide” parallels that of the
Ents, “As tall as trolls… clad with raiment or with hide of close-fitting grey and brown.” Moreover, the olog-hai were “strong, agile, fierce and cunning, but harder than stone,” also an apt description of Ents. And just as Orcs were bred in mockery of Elves,
Treebeard said that Trolls were bred in mockery of Ents.
To summarize: “
goblins”
are orcs.
The Hobbit is a children’s story – for Tolkien’s children, no less – and he used “goblins” instead of “orcs” when telling his children his story. Tolkien himself tells us this in “Nomenclature”. “Hobgoblins” I suppose would be “uruk-hai”, or at least the leaders of the goblins: larger, stronger, and more cunning that the rest. Sindarin
orch is feigned to be the origin of
the Common Speech orc and the Black Speech
uruk. All orcs are properly
uruk in Black Speech, but with the appearance of the
uruk-hai, the orcs themselves made a distinction between these greater orcs and those weaker and smaller of their kind, whom they disparagingly and derisively called
snaga “slave”.
That’s what makes sense to me from this material.