Like the cassock, it is a garment that was originally intended for outdoor use. Today it is worn over the cassock. Originally it was ankle-length but by the eighteenth century it was shortened to the waist and the sleeves were shortened and became known as the cotta. In the Roman Catholic Church it was trimmed with lace. This is sometimes called a staff or a crook.
Shepherds use it to keep their sheep together.
A servant following the commands of his or her master. A person following the argument of a wise person. A citizen following the laws of a self-governed city. A student following the teachings of his teacher. In a real sense this is how acolytes should consider their ministry around God's altar.