Ann Emmert Abbott
Sorry, Dorothy, I didn’t mean to confuse you. “Slug” was my shorthand term for the shorthand title that goes into the running head at the top of each page of your ms after the first page. (Don’t use the whole title, unless it is extremely short, like one word.)
Probably “slug” was what we called the story ID at the newspapers I worked for.
For example, suppose I wrote a novel titled PEACHES AND CREAM. My header might look like this: