mould: English has three words mould. By some way the oldest is ‘earth, soil’ [OE], which comes ultimately from the Indo-European base *mel-, *mol-, *ml- ‘grind’ (source also of English meal ‘flour’, mill, etc). Moulder [16] may be derived from it. Mould ‘form’ [13] is assumed to come from Old French modle ‘form, shape, pattern’.
This was descended from Latin modulus ‘small measure’ (source of English module), a diminutive form of modus ‘measure’ (source of English mode, model, etc). Mould ‘fungus’ [15] appears to have originated as an adjective, meaning ‘mouldy’. This in turn was an adjectival use of the past participle of a now obsolete verb moul ‘go mouldy’, which was borrowed from an assumed Old Norse *mugla. => meal, mill, molar, moulder; mode, model, mood
