suppedaneum

Etymology
From, neuter of , composed of +  +.

Noun

 * 1) a foot-support for a crucified person, projecting from the base of the cross
 * 2) * 2002: At the center of the O, a nimbed Christ is fixed to a cross with a large serpent coiled at its base, his feet on a suppedaneum. — Celia Chazell, Reading Medieval Images, ed. Thelma Thomas & Elizabeth Sears (University of Michigan 2005, p. 27)
 * 3) the platform in front of the altar on which celebrating priest stands