[stands2reason]

Typed from my Webster's 9th New Collegiate: Riding [ME-redying or trithing, alter. of (assumed) OE thriding, from ON thrithjungr third part, etc.] (1514) 1: one of three administrative jurisdictions into which Yorkshire, England was formerly divided 2: an administrative jurisdiction or electoral district in a British dominion (as Canada)

[Fury]

Typed from my Webster's 9th New Collegiate: Riding [ME-redying or trithing, alter. of (assumed) OE thriding, from ON thrithjungr third part, etc.] (1514) 1: one of three administrative jurisdictions into which Yorkshire, England was formerly divided 2: an administrative jurisdiction or electoral district in a British dominion (as Canada)

This seems to be right on the mark. They are officially called "electoral districts", but probably many folks refer to them (still) as ridings.

Thank you!