The English word mould has several different meanings – the Oxford English Dictionary lists no fewer than 13 separate senses associated with it.
Here, I will briefly examine the specific sense in which mould means a hollow container or pattern of a particular shape into which liquid or another soft material is poured and allowed to harden. This could be something as mundane as a mould for a jelly for a children’s birthday party, or, on a grander scale, the sort used in engineering processes whereby molten metals are poured or injected into the cavity of a mould (Americans typically write mold) in order to produce items like tools or mechanical parts (this is also called die-casting).
The word can also be used metaphorically, as in moulding someone’s character or destiny.
The etymology of this sense of the word is particularly interesting, not least because it turns out that mould, model and module were all three originally the same word, coming down to us from the identical etymological root: Latin modus “manner”. Specifically, these words were actually derived from the Latin diminutive form of modus, which was modulus.
This Latin diminutive ending, masculine –ulus feminine –ula, gives us other modern English words: for example, calculus is the diminutive of Latin calx “stone, pebble”, where the mathematical meaning comes from the fact that pebbles were used in reckoning on the abacus or counting board; and Latin formula, the diminutive of forma, referred to a small pattern or standard set of words for use in legal settings or rituals.
The question then arises of how the original order of the consonants in modulus remained the same in model but came to be reversed in mould. This occurred during the Middle English period, when the consonant sounds /l/ and /d/ in Old French modle swapped positions and the word became molde. By the 13th century, this new version was used in a figurative sense, but by the next century it was being used literally to refer to hollow casting forms for metal or food.
In fact, this type of change is a classic example of what is known in historical linguistics as metathesis. This is a common enough process in language change, and can give rise to words such as anemone erroneously being pronounced as anenome.
Of course, giving a particular type of change a label is not equivalent to explaining why it happened, but I am happy to say that linguistic scientists are not surprised if and when metathesis occurs. Speaking involves such a complicated process of coordination that it is not at all unusual if speakers do not get every sound absolutely right 100% of the time.
Suggested Reading
Discombobulated, chortle and the art of making up words
Diminutives
Diminutives are modified forms of words which are intended to indicate something small in size or age. They are often employed affectionately, such as when speaking to or about children. English can employ different endings for this, for example Johnny, doggie, duckling, lambkin, booklet, kitchenette, and hillock.
