Yom Kippur - Day of Atonement (יוֹם כִּפּוּר‎) The root for "kippur" is "kafar" (רפכ), from "kofer", meaning "to ransom / wipe clean" – to atone by offering a substitute. The Tanakh's use relates to the priestly practice of "wiping clean" by the sprinkling of blood, with blood itself seen as an ancient detergent-like cleanser.