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late 14c., "jaw, jawbone," from Middle French mandible and directly from Late Latin mandibula "jaw," from Latin mandere "to chew," from PIE root *mendh- "to chew" (cf. Greek mastax "the mouth, that with which one chews; morsel, that which is chewed," masasthai "to chew," mastikhan "to gnash the teeth"). Of insect mouth parts from 1826.
mandible man·di·ble (mān'də-bəl)
A U-shaped bone forming the lower jaw, articulating with the temporal bone on either side. Also called submaxilla.