Black's Law Dictionary (2nd edition)dictionaries

Horn

In old Scotch practice. A kind of trumpet used in denouncing contumacious persons rebels and outlaws, which was done with three blasts of the horn by the king’s sergeant. This was called “putting to the hornand the party so denounced was said to be “at the horn.4* Bell. See Hobninq

Source: Black’s Law Dictionary 2nd Ed (1910)