"The Legend of Sleepy Hollow": five little words, including a couple throwaways. Seems like it doesn't have much to say, but Irving sure knows how to pack a punch.
Let's start with legend. By calling the story a legend, Irving places it in history with other great legends, like Atlantis, the Fountain of Youth, or the Legends of the Fall. People have spent their whole lives searching for these places, but they never seem to find them. With his title, Irving adds Sleepy Hollow to this list—well except that, nowadays, we can find it with a quick Google Maps search.
Next up: Sleepy. The sleepiness of the title refers to both a very specific mythological place (check out "Setting" to find out where—cliffhanger!) and to the behavior of the people in the town. It's a sleepy, little town where nothing much happens and people spend their time dreaming.
Finally, there's the Hollow. Not that kind of hollow (though Ichabod's head just might be). The term Hollow is used to describe towns in the Appalachian states. That means we know right off the bat that this is an American story taking place on the East Coast.
Okay, now we know what it means, but why is this the title? Because "The Legend of Sleepy Hollow" is a story about a place. It's not about Ichabod, it's about Sleepy Hollow. And Irving wants us to know that before we even turn the first page.