BLACK DOG

n.1. a counterfeit silver coin made from pewter, a silver-gray metal consisting of tin, lead and sometimes other cheap metals. Black here refers to bad money and the term black dog for counterfeit silver coins was common in the early eighteenth century. 2. a depression of spirits, melancholy or illhumor, etc. This term is often used in the phrase black dog on one's back, used to describe a person who is depressed or sulky (with the idea that there is an invisible black dog sitting on his shoulders). This phrase dates from the 1700s and is a reference to the superstition that bad luck supposedly accompanies a black dog and that the sight of a black dog and her pups is an unlucky omen.