Q From Evan Parry, New Zealand: In composing an email to a friend, I used the phrase cottoned on, meaning I’d understood. It suddenly struck me that it’s an odd way to describe taking a liking to, or taking advantage of, or becoming a fan of, or coming to understand something. Where and how did the expression originate?
A It’s complicated, but I’ll try to unravel it for you.
We’re sure that the verb comes from the noun cotton for the plant and the fibre. This derives from Arabic qutn, because the plant’s homeland is the Middle East.
The very first sense of the verb was to raise the nap on cloth such as wool to draw out the loose ends of the fibres before shearing it to give it a smooth finish. It may have been because freshly woven cotton has a natural fuzzy nap that means it can be sheared without first having to artificially raise it. To call a fibre cotton at that time meant it had the finish of cotton, but was actually wool or linen or a mixture of linen and cotton. Confusingly for people who know Manchester as the traditional centre of the cotton trade (to the extent that in Australia and New Zealand Manchester means cotton goods such as household linen; it’s short for Manchester wares), in the sixteenth century Manchester cotton could be a type of woollen cloth.
By the middle of the sixteenth century the verb sense of cotton had become a figurative expression meaning to prosper or succeed. A writer in 1822 tried to explain it: “a metaphor, probably, from the finishing of cloth, which when it cottons, or rises to a regular nap, is nearly or quite complete.”
By about 1600, to cotton together or cotton with a person meant you got on well together. It has plausibly been suggested it came from the use of mixtures of cotton and other fibres in clothing. A little later, cotton up meant to strike up a friendship. In the early 1800s, to cotton to somebody implied that you were drawn or attached to that person. It may be that the idea here is how well a thread of cotton sticks to the surface of cloth. Cotton to was taken to Australia and became common there:
“My word! Dick,” Jim says, “it’s a murder he and Aileen didn’t cotton to one another in the old days. She’d have been just the girl to have fancied all this sort of swell racket, with a silk gown and dressed up a bit.”
Robbery Under Arms, by Rolf Boldrewood, 1888.
Around 1900 this became cotton on to and then cotton on, still in the same sense. Within a decade it was known both in Britain and the US and remains so in the latter country, though it is rather regional and feels old-fashioned or homely.
By the 1920s, cotton on had developed the last of the meanings that you mention, of coming to understand some matter. It’s not too surprising — if you can cotton on to a person, you can equally cotton on to an idea. The best clue I’ve found to its origin is in a glossary of English army slang used in World War One, published in Notes and Queries in December 1921. This included cotton on (to) in the sense “to understand”. We may guess that it evolved in Australia and was communicated to British and American soldiers during that war.