I am looking for a word or phrase denoting remoteness and great distance from human habitat, for the purpose of naming a cabin in the wilderness. I have already thought of "far cry" and "back of beyond". It would be good if the word or phrase was associated with a quotation or title from a book or proverb, but mostly it needs to resonate with the idea of a place "far from the madding crowd".
How about (ultima) Thule, a mediaeval term used to denote “any distant place located beyond the ‘borders of the known world’”?
It’s a town and former municipality in the north of Greenland as well, named for its remoteness.
Or perhaps, if you’re fond of comics, Faroffistan (from a 1958 Dumbo strip by Carl Fallberg and Paul Murry). In the Scandinavian translations of this strip, the word Langtbortistan (Danish)/Långtbortistan (Swedish) was coined, and this term has since become a common word in both languages to describe a more or less fictional, remote place.
How about one of the following:
I hope that at least one of these has the shade of meaning you're looking for
Timbuktu - a place that is unimaginably far away, completely foreign, or unreachable.
Even though Timbuktu is a real city in central Mali, it was (and still is) a term used to describe a far away place. It doesn't carry the meaning of a place far from human habitat, though. But it is certainly meant to imply a place far from major human habitat.
Outback - remote area, especially in Australia: a sparsely inhabited or wilderness region of a country, especially of Australia; The remote and usually uninhabited inland regions of Australia.
There is an interesting discussion at the link about the origin of the term outback, including terms like Never-Never (meaning the remoter parts of the outback), Black Stump, Beyond the Black Stump (and there are Black Stump Run and Black Stump Creek). Also Back of Beyond, as you mentioned.
You might consider Never Never Land, which is closely related to Never-Never.
Then there is the much less polite Bumf$%k, Egypt, which is described as someplace hard to get to and generally undesirable; the boonies or toolies. The middle of nowhere. It's where soldiers get sent when they are deployed, hence the scornful language.
Beyond the pale was covered very well in the linked ELU thread. Requoting from that thread: