The story
Coined by Thomas Henry Huxley in 1872 as xipho- + plastron. Superseded the earlier xiphisternum, a nominalised form of the French adjective xiphisternal, coined by Étienne Geoffroy Saint-Hilaire in 1818. The prefix is from Ancient Greek ξιφοειδής (xiphoeidḗs, “sword-shaped”), ultimately from ξίφος (xíphos, “sword”), in analogy with the xiphoid process at the posteriormost end of the human sternum.
Etymology from Wiktionary, CC BY-SA 4.0.