means A fuzzy fungus that grows on damp or decaying matter, or, separately, a hollow form into which liquid material is poured to set into a fixed shape.

from Two different words sharing one spelling. The fungus 'mould/mold' likely comes from Middle English 'moulen' (to grow musty), related to Old Norse 'mygla' (to grow moldy). The shaping 'mold' descends from Old French 'modle', from Latin 'modulus' (a small measure), the same family that gives us 'model' and 'module'. A third, older 'mold' meaning earth or soil comes from Old English 'molde' — the dust we return to.