Q From Peter Hill, Canada: I had never before heard the term epenthesis that you used the other week, so I looked it up on my computer dictionary. It gave its definition as “the insertion of a sound or an unetymological letter within a word, eg, the b in thimble.” Why did it indicate that the b was introduced into this word? Thumb has a b in it, although it is silent, so it seems logical that a thumb covering should also possess one!
A Be careful. Arguing by analogy is a dangerous matter, especially when applied to etymology.
There are many unetymological letters to be found in English words, of which the best known is the b in debt, which was added to reflect the word’s source in the Latin debitum, something owed, even though the word is actually recorded from the Middle English period as dette. Another is doubt, in Middle English douten, ultimately from Latin dubitare, to waver in opinion, hesitate.
Usually we can blame eighteenth-century grammar pedants for such changes, but in this case not — both debt and doubt began to be spelled with that intrusive and unnecessary b in the sixteenth century. The first example of debt cited in the Oxford English Dictionary is from the 1548 Book of Common Prayer: “To declare his debtes, what he oweth.” It was the influence of Latin spelling that caused the changes, though as far as we know the bs were never pronounced.
Another common cause of epenthesis has been shifts in pronunciation that have led to changes in spelling. For example, thunder has an added d (the Old English was þunor (the þ is the old character thorn, pronounced the same as the th in modern thunder). Empty has an epenthetic p, since the Old English was æmtig. (Modern cases of intrusive p include dreamt and hamster, though these aren’t reflected in the way they’re spelled because our orthography has long since become fixed.)
In other English words an epenthetic b has been introduced after m. Often, the b was interpolated when the ending -le was added to a stem that ended in m (crumble from Old English cruma; other cases include bumble, bramble, fumble, jumble, mumble and nimble). Once established, in some cases the root word (crumb for example) came to be spelled the same way by analogy, even though the b wasn’t pronounced.
Something similar happened with thimble. This comes from Old English þýmel. It was derived from þúma, a thumb, by adding the -le suffix, which in this case marked the names of instruments. So a þýmel was a device one used on the þúma. All very logical, but confusing to modern users, who generally put a thimble on a finger, not a thumb. The OED guesses that a leather thumb stall was the earliest form of thimble.
The first recorded uses of thumb and thimble don’t appear to support this move, since thumb is recorded first around 1300, about a century before thimble appeared. However, this may merely be an artefact of the records that happen to have come down to us. It would seem more likely from other examples that þýmel turned into thimble and thumb was afterwards respelled to match.