A hoodoo charm held to confer magical powers upon its possessor, including invisibility and the ability to triumph over sexual rivals. In the above song, the performer is suggesting that his girlfriend has been able to prevent abandonment by virtue of using his own black cat bone. As dispensed by some conjurers, the charm was represented as a bone boiled from a live black cat that made no reflection in a mirror (Puckett, 1925). An ex-slave noted: “First, the cat is killed and boiled, after which the meat is scraped from the bones. The bones are then taken to the creek and thrown in. The bone that goes up stream is the lucky one and should be kept” (Minnie R. Ross, as quoted in Born in Slavery). At the same time, the phrase was loosely applied to mean “just a bone they put in that hoodoo bag . . . [with] a piece of lodestone, some kind of red cloth; they got it mixed up together” (Willie Moore).
From Barrelhouse Words: A Blues Dialect Dictionary by Stephen Calt.