SKB wrote, regarding Shade's status as an orphan:
As others have hinted, it seems a natural narrative choice: Shade is pondering the hereafter and VN gives him a dead parent and a dead daughter to feed his ruminations
MR: I agree with this, and I think there are probably other discernable causes and effects which might be discovered via a wider study of that particular narrative choice.
SKB: There’s a natural but rather archaic link from “cedared” (populated by cedars) to “cedarn” (made from cedar wood); one sees a similarly antiquated link from “leather” to “leathered” and “leathern.” Why certain wondrous word-forms fade away, or remain tagged in dictionaries as poetic is beyond fathomage.
MR: It's just a coincidence, I'm sure, but the "aunts and orphans" thread and the Cedarn thread unite in Mrs. Browning's "Aurora Leigh," the protagonist of which loses her mother at four and her father at nine, and is shipped off to England to be raised by her predictably stern aunt. Here we find the following, a veiled reference to Tennyson:
Nor Belmore, for the unity of aim
To which he cuts his cedarn poems, fine,
As sketchers do their pencils; . . .
I don't think there is much significance in this for our reading of PF, though the opening lines of AL might have been written by John Shade:
OF writing many books there is no end;
And I who have written much in prose and verse
For others' uses, will write now for mine,–
Will write my story for my better self,
As when you paint your portrait for a friend,
Who keeps it in a drawer and looks at it
Long after he has ceased to love you, just
To hold together what he was and is.
That's precisely what "PF" is: an attempt by John Shade to hold together what he was and is.
I was curious how often, since Milton first used it, that cedarn appeared in poems. Of course it occurs in Coleridge, Tennyson and Matthew Arnold. But I was surprised to see that a particular combination, "cedarn shade," became something of a poetic cliche in the 19th century. See here:
Pass from the cedarn shade
To sands and heat. (Francis Bourdillon, 1894)
So sat the twain one autumn day
In the cool cedarn shade... (Wm. Sharp, 1884)
For priests the cedarn shade and mighty kings (Alexander Beresford-Hope, 1843)
Intense with spring, and flecked with cedarn shade (James Kenward, 1871)
The pagan haunts Idume's palmy shore,
And Moriah's hills, and Liban's cedarn shade (Robert Pearce, 1847)
Like bowers of beauty, with their blossoming woods,
And white-faced temples in the cedarn shade (Thomas Westwood, 1868)
and methought I knew
Havilah's cedarn shade, but dreamy dark
It fell around; (William Wilberforce Lord, 1851)
Now the picture of Sanchia and Melusine, two fair girls, standing together embraced under the cedarn shade... (Maurice Hewlett, 1910)
In a poetry review:
"Icicles and denned snakes and bears asleep, brightening beeches, and meadow rills, fire-flies and summer rain and cedarn shade accompany the seasons through the year." (Overland Monthly, 1887)
And finally, as confirmation that "cedarn shade" was indeed a well-known cliche, we have this from a prose passage in "Some Heroes of Travel," a book by W. H. Davenport Adams, published in London in 1880:
"Here they rested, in a 'cedarn shade,' until the gale had subsided."
There would be no meaning for those quotation marks if they did not signify a well-known phrase. Given this, I wonder if it is too far-fetched to allow the possibility that VN chose the name Cedarn because it was related, in his literary memory, to the word "shade." (And also, of course, to the Cedar Waxwing, which we've noted here before).
Interesting too that most of these uses of cedarn carry with them Milton's original context--a paradise or hereafter, Arcadian or Elysian.
PS. Jansy, "Ravenstone," of course, comes from the German Rabenstein, the place of the gallows, which is mentioned in Goethe's Faust. It's also mentioned in Byron's "Werner." Baring-Gould writes: "A German name for [the gallows] is the raven's stone, not only, perhaps, because raven's come to it, but because the raven was the sacred bird of Odin." Odin is easily tied the Erl-King, and round and round we go. In VN's translation of "The Eye" (but not in the original) he gives the boarder who rents Smurov's old room the name "Dr. Galgen," which also means gallows.