What is the X in X-mas?
1610s, from Latin crater, from Greek krater "bowl for mixing wine with water," from kera- "to mix," from PIE root *kere- "to mix, confuse; cook" (see rare (adj.2)). Used in Latin for bowl-shaped mouth of a volcano. Applied to features of the Moon since 1860. As a verb, from 1830 in poetry, 1872 in science. Related: Cratered; cratering.
crater cra·ter (krā'tər)
A circular depression or pit in the surface of a tissue or body part.