>This is a wonderfully old word, with serious history...

Funny, it doesn't make it into "Atomica" and Canada is only next door:
rid·ing1 (rî'dĭng)
n.
The act of riding.
Horseback riding.

In Yorkshire (NE England), before re-orgnasation of boundaries there were three ridings "North", "West" "East" as any fan of the Bronte sister will know. Riding meant third, as far as I am aware which why the county described in Winnifred Holtby's book was an invention.