My first association was to the Isle of Wight, but this is actually about "wight" as an archaic English word for "man" or "being", which goes at least back to Chaucer's "He nevere yet no vileynye ne sayde / In al his lyf unto no maner wight". In popular culture, it's probably best known from "Barrow-wight", the malevolent haunter of a barrow in an episode in The Lord of the Rings that didn't make it into the film. The phrase appears to have been lifted by Tolkien straight out of an 1869 translation of Grettis Saga (a.k.a. the Saga of Grettir the Strong), a section where Grettir and his colleagues go treasure-hunting in a barrow.
Then Grettir entered into the barrow, and right dark it was, and a smell there was therein none of the sweetest. Now he groped about to see how things were below; first he found horse-bones, and then he stumbled against the arm of a high-chair, and in that chair found a man sitting; great treasures of gold and silver were heaped together there, and a small chest was set under the feet of him full of silver; all these riches Grettir carried together to the rope; but as he went out through the barrow he was griped at right strongly; thereon he let go the treasure and rushed against the barrow-dweller, and now they set on one another unsparingly enough.
Everything in their way was kicked out of place, the barrow-wight setting on with hideous eagerness; Grettir gave back before him for a long time, till at last it came to this, that he saw it would not do to hoard his strength any more; now neither spared the other, and they were brought to where the horse-bones were, and thereabout they wrestled long. And now one, now the other, fell on his knee; but the end of the strife was, that the barrow-dweller fell over on his back with huge din. Then ran Audun from the holding of the rope, and deemed Grettir dead. But Grettir drew the sword, 'Jokul's gift,' and drave it at the neck of the barrowbider so that it took off his head, and Grettir laid it at the thigh of him.
- pp47-48, Grettis saga: the story of Grettir the strong, trans. Eiríkr Magnússon, William Morris, F.S. Ellis, 1869
But I admit I didn't run into "wight" anywhere as worthy, or even in Tolkien. I first remember it from the last of EE 'Doc' Smith's atrocious 'Lensman' series, Masters of the Vortex:
For his guardian against lighting had been a vortex-magnet at the moment when some luckless wight had tried to abate the nuisance of a 'loose' atomic vortex. That wight dies, of course- they almost always did-and the vortex, instead of being destroyed, was simply broken up into a number of widely-scattered new vortices.
Pulp authors were fond of these Sunday-best words (compare HP Lovecraft's fondness for words like "eldritch" and "effulgence") but it's hard to see what was going through Smith's mind to use this archaic word in his technophile space opera.
On brief research, I get the impression that "wight" underwent a decline and temporary revival in its long history of usage. Samuel Johnson's A Dictionary of the English Language (see 6th edition, 1766, Volume 2) cited examples from Shakespeare, Dryden, Butler and Milton, and defined it as "a person; a being" but with the qualification "Now used only in irony or contempt". Much the same is said in this 1819 gloss to Samuel Butler's late-1600s Hudibras: "The word wight was often used by our old writers to imply person, but it had become nearly obsolete in Butler's time, and he probably used it in a ridiculous sense, as we do at present, when we say, a luckless wight."
But "wight", in the context of "luckless wight" (a jocularity for "unfortunate person"), seems to have exploded as a cliché at the end of the 18th century: see Google Books Ngram Viewer.The first example I can find in print is in a poem, Sylvia and Colin ...
Oh stay ! oh stay!— I sue in vain
He's gone—O had I spoke more plain,
Ere he had fled my sight.
Ah ! charming youth; ah ! happy fair,
To be the charming COLIN's care,
And I a luckless wight.
- Sylvia and Colin. A pastoral. By a lady. Page 97, Scots Magazine, February 1761.
... but it soon turned up in the works of satirical writers - Laurence Sterne (1766) and Peter Pindar (1794) - and by the mid-1800s, everyone was using it to droll effect (see Google Books) such as in this Punch parody of Shakespeare:
I know a bank wherein my wild cheque goes,
Where if they'll pay it, goodness only knows!
There I've one pound fifteen.
There creeps some luckless wight
Bills to present, when "no effects" they write.
- page 149, Punch, Volume 13, 1847
But it wasn't all comic. The phrase turns up in at least two translations of Dante's Inferno, in Canto XXII, where it's used as a translation of "sciagurato". (My OUP edition translated by John D Sinclair uses "hapless wretch", and the Henry F Cary translation on Bartleby.com says "wretched soul". I suggest "poor bastard").
E io: «Maestro mio, fa, se tu puoi,
che tu sappi chi è lo sciagurato
venuto a man de li avversari suoi»
- Dante, Inferno, Canto XXII
Then I: "O Master mine, inquire, I pray,
what luckless wight hath fallen thus
into the demons' paws."
- page 128, Canto XII, Inferno, trans. WP Wilkie, pub. Edmonston and Douglas, 1862
And I: "My Master, see to it, if thou canst,
That thou mayst know who is the luckless wight,
Thus come into his adversaries' hands."
- page 94, Canto XXII, Inferno, trans. HW Longfellow, pub. B. Tauchnitz, 1867
Still, by the early 20th century, it had become a joke. Joseph Fitzgerald, in his 1901 Word and phrase: true and false use in English, commented:
The derivatives of Man in English are very few, and they were all in use before the language lost its species name for the human individual: they are formed from Man or Mann, the word meaning male human individual, and hence are rightly applicable only to the male individual, his characters, his works; these derivates are manly, manlike, manful, manhood, the verb to man, and the participle form, unmanned. But there was once in the language of the people, and still is in the language of poets, a word which answered well to Mensch, homo, anthropos. That word is Wight. But the comic poets have made "wight" their exclusive property, so that even the phrase, "luckless wight," i.e., a human creature in misfortune, no longer suggests to us compassion, fellow-feeling, but mild contempt at best.
Google Books Ngram Viewer shows "luckless wight", while declining, persisted well into the 20th century. Knowing that EE Smith was born in 1890 and was widely read - see Wikipedia - I guess goes some way toward explaining how he picked up this archaic turn of phrase. It still doesn't explain why he had the tin ear for prose to use it in such an inappropriate context.
Addendum: Rodger C at the Language Log thread has added what I didn't know: that the original word for barrow-wight in Grettis Saga is "haugbúi" (haug = mound, búi = dweller). This nicely explains why a number of historical sources mention a fabled goblin inhabiting a tomb in Orkney was called the "Hogboy".