(Latin, derived from lavare, "to wash")
A labrum was a water-filled basin, originally used in farming (usually to press grapes in), but more commonly known for its use in Roman baths, where a labrum filled with cold water was placed, so that visitors to the calidarium might sprinkle themselves with cold water if they got too hot.
In Christian times, the labrum was also used for a washing ritual, symbolically cleansing the celebrant. This function is reflected in the vessel filled with holy water placed in Catholic churches to this day, and to a lesser degree by the baptismal font in all Christian denominations using water in their rituals.