When/how "Timbuctoo"~="Podunk"~="Nowheresville"~="Buttfuck, Idaho"; Other languages have sim. names?

On seeing this, I instantly bet myself $50 that by “I’ve come across several times” you meant “I enjoy using this expression but I totally made it up myself”. But what do you know:

So now I owe myself half a C-note, and I haven’t got it. I hope I’ll be willing to wait till payday.

The remotest place in the world is surely Easter Island. It is thousands of miles in any direction to the nearest land, and each of those lands is, itself, proverbial for remoteness:

Way way to the west are the Pitcairn Islands, where the Bounty mutineers beached their ship-- and weren’t found again for decades.

Way way to the north are the Galapagos Islands, where hardly any forms of life made it except finches and turtles, giving Darwin a famous lesson on how creatures diversify.

Way way to the east are the Juan Fernandez Islands: in English one is called Alexander Selkirk island, after a guy who quarreled with the captain and asked to be put ashore, not realizing it would be years before any ship came there again; his account of how he survived his marooned condition inspired “Robinson Crusoe” by Defoe, so the other island in the group is Robinson Crusoe island; but in Spanish they were just named Mas-a-tierra and Mas-afuera (More-toward-land and More-out-there) by Juan Fernandez who tried to make it a colony and failed.

And way way to the south are the Thurston Islands, off a stretch of Antarctic coasts that none of the southern explorers had gone to, until Byrd flew over it in his plane; the Thurston Islands were absolutely the last bit of land added to the world map.

And Easter Island is thousand of miles from any of those places.

If you’re talking about inhabited places Tristan De Cunha takes the prize as the most remote inhabited island and archipeligo.

It’s 2400 km from Tristan to St. Helena, which is also famous for being remote, and that is further than the 2000 km from Easter Island to Pitcairn; but in the other direction it is 2800 km to the Cape in South Africa, and that is a busy place, whereas it is about 3000 km from Easter Island to Juan Fernandez or Galapagos or Thurston, all of which compete with Pitcairn and St. Helena for being, themselves, Boondock Podunk Bumfuck-Egypt Timbuktu places.