curb / kerb

pic from
(AmE) What's up with the spelling kerb? This is one of those topics that I *thought* I had blogged about. But no!

BrE has kerb for the edging alongside a road or path and curb for the 'restraint' verb (as in curb your enthusiasm). AmE uses curb for both.

In general, there are more homophones for which BrE differentiates spellings and AmE doesn't than the other way (a)round. This is not particularly surprising, since spelling differences are generally in the direction of AmE being easier to learn than BrE (that was Noah Webster's first priority in promoting new spellings).

But the point I try to highlight when I talk about spelling differences is: most American spellings were not invented in the US. There have always been spelling variations. And that's well illustrated by this case.

Spelling the 'edge' noun

Kerb is the newer spelling—albeit, still hundreds of years old. The first c- spellings for the noun are from the 1400s, following the spelling of the French word from which it ultimately derives: courbe, for 'curved'. Before paving was so common, there were lots of other uses of curb, including some that referred to different kinds of curved edges around things. Occasionally (from the 1700s), these were spelt with a k, but the c was much more common. It's only in the 1800s that the k spelling becomes firmly associated with 'an edging of stone (etc.) along a raised path'. In the age of industriali{s/z}ation, such edgings would have become more commonplace.

The OED's entry for kerb gives the etymology as 'variant of CURB, n., used in special senses'.  This looks an awful lot like what happened with tyre. Tire had become the usual spelling for wheel-related meanings (though tyre had been around too), but when the pneumatic variety became available, BrE started using a less-common spelling for the word, in order to differentiate the old kind of thing from the new kind of thing.

Since the spelling changed after AmE and BrE had parted ways (and before the advent of fast communication between the two), there was no particular reason for Americans to experience the new spelling much or to use it. There was a perfectly good spelling already.

Verbs and nouns and nouns and verbs

A covered curb chain on a horse
The 'restrain' verb is always curb in both countries, and that came from a noun curb. Both were originally about restraining horses with a chain or strap that goes under its jaw. Metaphorically, that extends to other things you'd like to 'rein in'. So you can curb your appetite or ingest something that will act as a curb on your appetite, but you'd never spell those as kerb (unless spelling isn't your strength).

But another verb meaning for curb has come up in AmE, which takes advantage of the homography of  the 'restrain' verb and the 'stone edging' noun.  I first recall being aware of these signs in the late 1970s,  when New York City's first (orig. AmE) pooper-scooper laws were in the news.

snapped in NYC in 2013

But Curb Your Dog signs go back to the 1930s. Back before anyone had to pick up their dogs' poo(p), owners were encouraged (or required) in NYC to make dogs "do their business" at the edge of the (AmE) sidewalk (or maybe in the gutter) so that the mess would be out of pedestrians' (and plants') way. (There's a nice little explainer here.) In this case, you are taking your dog to the curb/kerb, but also curbing their tendency to relieve themselves in inconvenient places.

Bonus vocabulary

Not something I knew till Simon Koppel pointed it out to me, but there are technical terms for those places in the (BrE) pavement/(AmE) sidewalk where the curb/kerb is lower to make it easier to cross the road/street, especially for those using wheels to do so.  In AmE these are curb cuts and in BrE dropped kerbs. 


  1. Nothing to do with kerb/curb, but your opening sentence reads strangely to me.
    I think maybe you should mark "What's up with...?" in the way use it as 'AmE'.
    To me (Southern English, 50s) it means "What's wrong with...?", and not "What's going on with...?".

  2. In varieties of Irish English which preserve the historical distinction between the vowel of TERM and the vowel of NURSE, some speakers pronounce "kerb" with the TERM vowel. This must have originated as a spelling pronunciation, since "kerb" and "curb" are, as you say, historically the same word.

    1. Really interesting, thanks!

    2. BrE, Scot, late 60s. I haven’t spent much time in Scotland for a while, but I expect that we still pronounce kerb with the NURSE vowel. But then, we also pronounce “herd” as HURD. I’m sure there are many other examples.

    3. Depends what part of Scotland you come from. I would say "herd" with a narrow vowel and rolled "r"; "curb" with the vowel of "but" and again the rolled "r". I'm from Ayr.

    4. I am originally from just south of Ayr. Thinking about this, words like bird or third also sound pretty much like BURD, THURD etc. Even milk can sound like MULK. However, we do roll our r’s.

    5. My Scottish wife would agree that 'curb' and 'kerb' are most definitely (or 'definAtely to quote some Scots) are not homophones. One has an 'e' and other has a 'u'.
      I was at school in Lanarkshire, and I had a Maths teacher who repeatedly corrected pupils' pronunciation of 'third' when they said 'thurd', to make them emphasising the 'i' sound more to rhyme with 'thin'. It is worth remembering that for Spike Milligan, 'absurd' and 'bird' do rhyme.

    6. No difference in pronunciation between the two in AusE either. I always did like Spike!

  3. As an American from the south, I have never heard curb used as in "curb your dog." Is it specific to New York City?

    1. I don't know if any other cities have since picked it up, but it's very much a NYC thing.

    2. Anonymous in New Jersey06 June, 2020 05:37

      We use “curb your dog” in northern New Jersey. But I definitely wasn’t familiar with it during my South Jersey youth.

      Oddly enough, throughout quarantine, I have been thinking a lot about the origins and meaning of “curb” in that context. (I take a lot of walks these days.) Years ago, BF (who is North Jersey born and bred) gave me the “take your dog to the curb” explanation. I thought that he was being ridiculous because everyone I know picks up their pets’ poo.

      It seems I may have some crow to eat.

      Thanks for that, Lynne.

      – AiNJ

    3. I remember from my childhood in the US, reading books about owning and training dogs (I wanted a dog!). This would have been around the mid-1960s, so the books would have been written around the late '50s to early-mid '60s.

      They all mentioned curbing your dog, with instructions on how to train the dog to do this. It was considered a mark of a considerate owner -- whatever the dog did would be out of the way of pedestrians, and would be washed down the gutter with the next rain. The idea of picking up dog poo and taking it home for disposal was literally unthought-of. (For a start, I suppose that depends on secure plastic bags being cheap and plentiful.)

      I believe guide dogs are still trained to curb themselves if they have to go while walking along a road, as the blind person is not expected to pick up whatever the dog leaves behind.

  4. In Australia those accessible kerbs are "kerb ramps".

  5. They can also be rollover kerbs in Australia.


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AmE = American English
BrE = British English
OED = Oxford English Dictionary (online)