Excalibur (n.)

King Arthur's sword, c. 1300, from Old French Escalibor, corruption of Caliburn, in Geoffrey of Monmouth (c.1140) Caliburnus, apparently from Welsh Caledvwlch probably a variant of the legendary Irish sword name Caladbolg which might mean literally "hard-belly," i.e. "voracious." For first element, see callus; for second, see belly (n.).