I can't find this by searching and it might be I'm just using the wrong terms.
In the ACP you can change the forum name and description, and whatever you set the forum name to (see example image) will be "[That name] - Index" when on the Index page. I don't want to display a forum name or description (it's embedded in the header image instead), and you can do that by just leaving those fields blank, but if you do that your Index page will display on the tab/window as " - Index", and that isn't really ideal.
Hopefully the pictures help to make my silly problem understandable.