I remember there was a traditional rumour that if you weren't good then at Christmas you might get lumps of coal in your stocking instead of presents. But I think it would have been Father Christmas putting them there.

I think in Europe at any rate the use of black in proverbs and epithets - black moods and so forth - don't have anything historically to do with black people, they are tied up with the idea of the dark as being a time of danger, carrying over into the term black.