Belief in various superstitions has emerged as a motif in the novel. What is a "Hot steam"?

“Haven’t you ever walked along a lonesome road at night and passed by a hot place?” Jem asked Dill. “A Hot Steam’s somebody who can’t get to heaven, just wallows around on lonesome roads an‘ if you walk through him, when you die you’ll be one too, an’ you’ll go around at night suckin‘ people’s breath-”