Why is a match between two teams from the same town called a "derby"? | Notes and Queries

Why is a match between two teams from the same town called a "derby"?

Andrew Laird, Glasgow

• A slight correction to the question - these days a derby is not necessarily a match between two teams from the same town, but just the nearest and bitterest local rivals. To qualify, the two teams in question need to have some prospect of ever playing each other on a regular basis (for example, Newcastle United and Gateshead are not considered great local rivals despite being closer together than Newcastle and Sunderland, as the clubs are too many divisions apart).

  Anne, Durham, England