1911 Encyclopædia Britannica/Asperges
ASPERGES (“thou wilt sprinkle,” from the Latin verb aspergere), the ceremony of sprinkling the people with holy water before High Mass in the Roman Catholic Church, so called from the first word of the verse (Ps. iv. 9) Asperges me, Domini, hyssopo et mundabor, with which the priest begins the ceremony. The brush used for sprinkling is an aspergill (aspergillum), or aspersoir, and the vessel for this water an aspersorium. The act of sprinkling the water is called aspersion.