This is something very odd I have noticed in some older books, most recently in "Crime and Punishment" by Dostoyevsky. Place names, when not specifically essential or well-known, are made up of one letter followed by a line of underscores (i.e. "X_____"). I think I recall reading something similar in another older work, possibly by Jane Austin?
Apologies if this is a duplicate; I've searched quite extensively and can't seem to figure it out. I don't know a name for this, so can't search easily for it.
Best Answer
It's censorship. The notes in one edition say:
(See also Why are place names obscured in Charlotte Brontë's The Professor? for a fuller explanation about the use in literature.)
Much like how we now usually use asterisks, older works typically used em dashes (not underscores, which are lower on the line).
The New English Dictionary (1887), predecessor of the Oxford English Dictionary, says this of "bloody":
Because (or in spite of?) the subject, Grose's Classical Dictionary of The Vulgar Tongue also has plenty of examples. Here's one where "turd" is censored:
Further down on the page, "**** hooks" is defined as "fingers", so asterisks were also sometimes used, particularly when all the letters were censored as to prevent it from looking like a regular em dash. (The omitted word here is "cunt".)