Sure, it kind of seems straight-forward at first, but Shmoop's here to tell you that actually there are a couple of things to notice about this title. First off, it's got a double-entendre in there. (A double-what, you ask? Not to worry Shmoopsters, we're always ready with a little vocab for you. "Double entendre" is French for "two meanings." Like, a word or phrase or whatever that has more than one meaning. It's got two of them.)
The double meaning here comes from the word idiot, which, believe it or not is exactly the same in Russian (except the stress is on the "o" and not the first "i"). On the one hand, the word meant back then what it still means today: dummy, numbskull, dimwit, or moron—you get it, basically "a stupid person."
On the other hand, this is the word that used to be a medical term for a mentally handicapped patient. The joke of course, is that although Myshkin starts out and ends as the latter, and is constantly assumed to be the former, he is actually the shining beacon of intellectual truth and beauty. So, irony.
Another way to go with this title is to compare it to all those other 19th century novels which are named after characters (Madame Bovary, David Copperfield, Emma, Anna Karenina). Why isn't this novel titled "Myshkin," as Dostoevsky originally intended? Why does Dostoevsky want us to focus on the way others perceive Myshkin right off the bat with the title?