1
general::
One is in trouble, disgraced, or discredited, as in If they find out I broke it, my name will be mud, or If his estimate is completely wrong, his name will be mud. A popular theory for this expression's origin derives it from Dr. Samuel Mudd, the physician who was convicted as conspirator after he set the broken ankle of President Lincoln's assassin, John Wilkes Booth. But the expression was first recorded in 1823, when mud was slang for a stupid person or fool, a usage dating from the early 1700s. Later the term mud simply alluded to discredit.
American Heritage Idioms