1808, coined in Modern Latin by its discoverer, English chemist Sir Humphry Davy, because it was present in the mineral barytes "heavy spar" (barium sulphate), so named by Lavoisier from Greek barys "heavy," from PIE root *gwere- (1) "heavy." The metal is actually relatively light. With chemical ending -ium. Related: Baric.
It forms all or part of: aggravate; aggravation; aggrieve; bar (n.4) "unit of pressure;" bariatric; baritone; barium; barometer; blitzkrieg; brig; brigade; brigand; brigantine; brio; brut; brute; charivari; gravamen; grave (adj.); gravid; gravimeter; gravitate; gravity; grief; grieve; kriegspiel; guru; hyperbaric; isobar; quern; sitzkrieg.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit guruh "heavy, weighty, venerable;" Greek baros "weight," barys "heavy in weight," often with the notion of "strength, force;" Latin gravis, "heavy, ponderous, burdensome, loaded; pregnant;" Old English cweorn "quern;" Gothic kaurus "heavy;" Lettish gruts "heavy."
transuranic metallic element, 1942, from Pluto, the planet, + element ending -ium. Discovered at University of California, Berkeley, in 1941, the element was named on suggestion of Seaborg and Wahl because it follows neptunium in the periodic table as Pluto follows (or followed) Neptune in the Solar System. The name plutonium earlier had been proposed for barium and was used sometimes in this sense early 19c.