A shebble is a "shit pebble" that was once a dingle berry that has now dropped from your ass to the floor and/or ground.
Parent: "WTF, who left this shebble on the kitchen floor?"
Child: "That isn't a shebble... uh, it must be a chocolate chip."
Parent: "Ahh, hell no, that's chocolate shit...a shebble!!!, get some clorox and clean this f'in shit!!!"