Molybdenum's name is a fossil of an old error. Its chief ore, molybdenite, is soft, grey and greasy to the touch, and it so resembled both galena, the lead ore, and graphite that all three were lumped together under names derived from molybdos, the Greek word for lead, and used interchangeably as marking materials. Only when Scheele analysed molybdenite did it become clear that it contained neither lead nor carbon but a distinct new metal, which nonetheless kept the misleading name. Molybdenum has no alchemical or symbolic tradition of its own; its story is one of disentangling substances that looked alike, and its name is a lasting reminder of the pre-modern difficulty of telling one grey mineral from another.
The confusion molybdenum's name preserves has a curious counterpart in biology: the enzyme nitrogenase, which lets certain bacteria fix atmospheric nitrogen into a usable form without any industrial Haber-Bosch plant, depends on a molybdenum-containing cofactor at its reactive centre, so the element chemists once mistook for lead turns out to be indispensable to the natural nitrogen cycle that sustains most of the planet's soil fertility. Graphite, molybdenite's other historical look-alike, was itself long called black lead or plumbago for the same reason, and only careful nineteenth-century chemistry finally separated the three greasy, grey, superficially similar minerals into carbon, molybdenum and true lead.