Scarlet Letter- Beetle-Browed?

It means "sullen, scowling, unfriendly-looking"--which fits a jail. Or the original meaning was "bushy, overhanging eyebrows." Don't know how that would fit a jail, but maybe the rest of the description in the book mentions an overhanging roof or an overhanging beam over the door? I read it, but don't remember a lot. Nothing I looked at explains what a beetle has to do with it. If bugs have brows, that's news to me.