"stone chisel," 1715, from a Latin ghost word (apparently a misprint of certe) in Job xix:24 in Vulgate: "stylo ferreo, et plumbi lamina, vel celte sculpantur in silice;" translated, probably correctly, in KJV as, "That they were graven with an iron pen and lead in the rock for ever." But assumed by others to be a genuine carving tool, partly because it was in the Bible, and thereafter adapted by archaeologists as a name for a class of prehistoric implements.
also Kelt, c.1600, from Latin Celta, singular of Celtae, from Greek Keltoi, Herodotus' word for the Gauls (who also were called Galatai). Used by the Romans of continental Gauls but apparently not of the British Celtic tribes. Originally in English in reference to ancient peoples; extention to their modern descendants is from mid-19c., from French usage.