It’s KERB! If you mean the thing between the road and the pavement.

[GETTINGLIKEMYMOTHER]

Unless you’re American, anyway.
‘Curb’ means ‘restrict’.

I've long maintained that you could say, "How are your haemorrhoids?" in Italian and it would sound romantic as long as you didn't know what it meant. (You know which word I've had to check in the dictionary before I pressed 'Post'.) Oo, I got it right!

In the UK, in 1850, was it kerb or curb?

Kerbs weren't invented until 1878 by Johannes Kerbowić, an immigrant from Latvia

Kerb comes from engineering, it is separate to and strengthens the edge of a paved road to stop it cracking and breaking at the edge if vehicles go to the edge.
A curb chain is part of a bridle to make it easier to control a strong horse.
IMO

You’re right OP.

I think you’ll find that’s, Knut….
😁

If you want to be totally factual from a highway engineering perspective, in the uk it is a kerb that separates the footway from the carriageway. (A ‘kerb’ also refers to the individual bits of concrete or stone that form the kerb)
Pavement refers to the materials that make up the carriageway, and a footpath is a pedestrian route that is not adjacent to a carriageway eg. the path that goes across a field.