A typical behavior or habit that’s been in place for quite a while, is — or at least can be — called a “custom.” It can apply to one person: “He never gave up his custom of going to business in a silk hat and a Prince Albert coat” (1938) or practically the whole human race: “The despotism of custom is everywhere the standing hindrance to human advancement“ (1859).
The word arrived in English around the year 1000 or so, but it’s not entirely clear where it came from. That’s because the possible sources are all pretty much the same. Anglo-Norman had “costume,” Old French offered “coustome,” and Old Occitan, Catalan, Portuguese, and Italian all had very similar words at the very same time.
As soon as it appeared in English, though, the use of “custom” was established in the customary way. Except that the French version was adopted a second time as “costume.” And although the original meaning was there from the beginning and has never really changed, “custom” has taken on additional meanings now and then. By the 1300s, “custom” also meant a law, or something that had the force of law (“Lawes þere beoth and costomes þat habbethz euere beon i-holde”).
Around the same time rent payments began to be called “customs” as well. This was probably a public relations stunt by the landowners; if the tenants asked “why do I have to pay you just to live here,” they could say “come on, it’s always been our custom, and we’re living in Medieval England, which is a very traditional society. So pay up.”
The landowners, of course, were the nobles who also (in different cliques) made up the government, such as it was. So when it occurred to them to put a tax on stuff being imported, they used the same word. That’s why we still have to go through “customs” when traveling internationally. Bureaucrats customarily follow the custom of using the customary word “Customs.”
The idea that habits are in charge is also behind the development of “customer.” Although it now applies to anybody who shops anywhere, at first you were only a “customer” if you returned to the same shop repeatedly. In that sense it was pretty similar to the feudal tenant who told someone — who might want to move in on the same land — that the place wasn’t open to new arrivals because the existing tenant was the “customer.”
By the 1700s, some shopkeepers and craftsmen had noticed that their customary customers would often pay extra for something made especially for them. Something “custom-made,” in other words. Or actually, come to think of it, that’s the same word. “Custom work” and “custom made” were, paradoxically, adopted to mean things created just once, for just one person. Except that in England, where the practice first arose, they found “custom” to be less than customary and decided to use “bespoke” instead. Maybe they used that because in describing exactly what should be delivered, speaking was customarily involved.
And remember “costume?” That arrived in English around the 1600s, from the same French word that “custom” was at least partly based on. At first it was applied in the art world, and meant the standard style of a type of art, or furnishings, or style of clothing, which is the place it finally stuck. “Costume” was even applied to literature for a while, but that usage never became customary.
