Outer Mongolia and Timbuktu are often used as shorthands in English for somewhere remote and inaccessible. But why exactly do we use these two places specifically?
Well, the simple answer is that they’re quite far away from English-speaking countries. Outer Mongolia was a term previously used by China to refer to what, basically, is now the country of Mongolia. Inner Mongolia is an autonomous region of present-day China, hence Outer referring to the fact that the northern Mongolia is outside the borders of China.
Of course the Outer in the name helps to make the place sound more remote, and is one of the main reasons we use Outer Mongolia as a shorthand for remote places in English. Funnily enough, the Mongolian language does something similar. The country of Mongolia is sometimes referred to as ar mongolia, meaning North Mongolia. But, ar evolved to also mean back in terms of any spatial entity from a mountain to a yurt, and in contrast to Inner Mongolia (or Southern Mongolia), Outer Mongolia could be perceived metaphorically as the backward northern side of a mountain, in contrast to the more advanced south.
Timbuktu is a quite interesting place, in the sense that a lot of people don’t think it exists, even though it’s a real city in modern-day Mali. The city gained a sense of mystery and distance in Renaissance Europe, largely thanks to accounts of the writer Leo Africanus. He and other visitors to the city emphasised its wealth and grandeur, as it was so far away for most denizens of Europe, it gained a mythical status, and came to be considered by many to be a kind of El Dorado or Atlantis, too good to be true.
For English speakers in particular, I think there’s something about the name that simply doesn’t sound real. Maybe it’s because each syllable on its own sounds like an English word (Tim, book, to/too/two!) Maybe it’s something about it ending in a long vowel sound, which isn’t so common in multisyllabic words.
But if you didn’t before, now you know that these two places are real, so if you do ever get sent to either, it won’t be so bad! Better than Coventry anyway.