Black as the hobs of hell

[Anniestogs]

What does this mean

[Quizmonster]

In the old days of cooking over an open fire, fireplaces were usually fitted with metal plates which could swing inwards over the heat or outwards away from it. Obviously, these became blackened over time and housewives used to spend hours cleaning and black-leading them. Obviously, the idea behind the saying is that the hobs in hell are particularly black because of the intensity of the fires there to punish sinners. In other words, very black indeed!

[Bellringer]

A Hob is a Hobgobling, and those from Hell were supposed to be black.
There are several places in North Yorkshire called Hob Hole, where a hogobling was upposed to live.
I suppose to the rest of the world they became Goblins but to Yorkshiremen they became Hobs.
That's Yorkshire for you.