What does Elm depict in A Nightmare on Elm Street? Does Elm tree represent something bad in the horror context?
Elm Street is one of the most common street names in the United States. If you exclude numbers (because numbers in a title are strongly connoted to having several in a series, whether it's streets or movies), the most common names are Park, Main, Oak, Pine, Maple, Cedar, Elm. So “Elm Street” has a “generic street” feel to it.
In fiction, Elm and Pine have traditionally dominated over the other tree names that are more popular in real life. Park is even above, but the word “park” has connotations (of nature, empty spaces, that kind of stuff) that “elm” doesn't have. This points towards Elm or Pine as a generic street name for a movie.
I've always seen it as just a very generic suburban name. There's a complete difference in tone and setting between (for example) A Nightmare on 5th Ave, A Nightmare in the Bronx, and a nightmare in peaceful suburbia.
To my knowledge there's nothing deeper to it, and my guess is that it just helps set the tone.
The wiki page says that maybe a 1968 student film project made by students of Craven's at Clarkson University inspired the movies. The student film parodied contemporary horror movies, and was filmed along Elm Street in Potsdam, New York.
I'm not sure if it's true or not, maybe it was just for the tone, like Stephan Muller said.
Craven decided to make A Nightmare on Elm Street after reading a series of L.A. Times articles about a group of teenage Khmer immigrants who, after moving to the U.S. from refugee camps, died in their sleep after suffering from disturbing nightmares.
There was also sleep paralysis experiments conducted in the 1970's by a doctor named Ravenscroft that lived on Elm Street.