https://www.grubstreetproject.net/places/90234/
>Black Mary's hole
>the name believed to be a degeneration of Blessed Mary's Well; the whole process of naming is an apt token of the darkening fate of London's springs. Other derivations have been suggested. The well may have belonged to the convent of St. Mary's, Clerkenwell, where the Benedictine nuns wore their familiar black habits. It may have been the property of a woman, Mary, who owned a black cow or alternatively by a black woman of the same name. It may have been dedicated to the "black Madonna," the Virgin depicted in the early medieval period with dark skin.
so this black bitch probably didn't even exist