‘Below the stone setts and pobbles of the wall’s apron …’

Couldn’t find this ‘pobble’ in the 600,000 words of the OED, until I realized it must be referring to ‘setts and cobbles’.   A ‘sett’ is a cobblestone and the two are often mentioned together.

I prefer ‘pobble’ which must be a pebble-cobbled cobblestone.  Or a fortuitous typo?

All sett?

Source: Henry Williamson, Tarka the Otter: His joyful water-life and death in the two rivers, illus. C.F. Tunnicliffe (Harmondsworth: Puffin Books, 1976 (1927)), p. 191