zircon (n.)

1794, circon, also jargon, new name given in chemistry to jacinth, from German Zirkon (Klaproth, 1789), which probably is from 18c. French jargon, a vague mineral word used of high-quality diamond-like gemstones; it has been traced to Medieval Latin jargonce, which is of uncertain origin. Compare Italian giargone, from the same source.