mold n.1

also mould, "hollow pattern of a particular form by which something is shaped or made," c. 1200, originally in a figurative sense, "fashion, form; nature, native constitution, character," metathesized from Old French modle "model, plan, copy; way, manner" (12c., Modern French moule), from Latin modulum (nominative modulus) "measure, model," diminutive of modus "manner" (from PIE root *med- "take appropriate measures").

By c. 1300 as "form into which molten metal, etc., is run to obtain a cast." By 1570s as "a form of metal or earthenware (later plastic) to give shape to jellies or other food. Figurative use of break the mold "render impossible the creation of another" is from 1560s.

also mould, "minute, furry fungus," especially the types growing on neglected food and decaying organic matter, c. 1400, molde, probably from moulde, past participle of moulen "to grow moldy" (early 13c.), related to Old Norse mygla "grow moldy," possibly from Proto-Germanic *(s)muk- indicating "wetness, slipperiness," from PIE *meug- (see mucus). Or it might have evolved from (or been influenced by) Old English molde "loose earth" (see mold (n.3)).

"fine, soft, loose earth," Old English molde "earth, sand, dust, soil; land, country, world," from Proto-Germanic *mulda (source also of Old Frisian molde "earth, soil," Old Norse mold "earth," Middle Dutch moude, Dutch moude, Old High German molta "dust, earth," Gothic mulda "dust"), from PIE root *mele- "to crush, grind." Specifically, since late (Christian) Old English, "the earth of the grave." Also, from c. 1300 as "earth as the substance out of which God made man; the 'dust' to which human flesh returns."

The proper spelling is mold, like gold (which is exactly parallel phonetically); but mould has long been in use, and is still commonly preferred in Great Britain. [Century Dictionary, 1897]

also mould, mid-14c., "to mix, blend (something) by kneading;" late 14c. "to knead (bread), form into a particular shape," from mold (n.1). Figurative sense (of character, etc.) is from c. 1600. Related: Molded; molding.