fluor (n.)

1660s, an old chemistry term for "minerals which were readily fusible and useful as fluxes in smelting" [Flood], from Latin fluor, originally meaning "a flowing, flow," from fluere "to flow, stream, run, melt" (see fluent). Said to be from a translation of the German miners' name, flusse. Since 1771 applied to minerals containing fluorine, especially calcium fluoride (fluorspar or fluorite).