WHY IS A SPORT DERBY CALLED "A DERBY"?

My grandson, who has an interest in football (as well as other things!), ask me this question. WHY IS A SPORT DERBY CALLED "A DERBY"?

There are two thoughts!! One theory is that the phrase comes from the Derby horse race which was founded by the Earl of Derby in 1780. 

At a dinner party in 1778 held on his estate, The Oaks in Carshalton in, Lord Derby and his friends planned a sweepstake horse race, won the following year by Derby's own horse, Bridget. The race, The Oaks, has been named after his estate. At a celebration after Bridget's win, a similar race for colts was proposed and Derby tossed a coin with Sir Charles Bunbury, for the honour of naming the race. Derby won, and the race became known as the Derby Stakes. Bunbury won the initial race in 1780 with his horse, Diomed; Derby himself won it in 1787 with Sir Peter Teazle. His racing colours were black with a white cap. His influence on racing has been described as "crucial".

The Derby is held at Aintree, near both Liverpool and Everton’s football grounds. The two clubs grounds are at nearby Anfield and Goodison Park respectively.  These are famously separated only by Stanley Park, which was then owned by The Earl. Some believe the phrase originated from a match between Liverpool and Everton in 1914. The first match between the two Merseyside clubs was on 13 October 1894, so maybe the word, which involved two close competing teams from Merseyside. came from the horse race? It is the longest running top-flight derby in England and has been played continuously since the1962-3 season.

The other thought to the name's origin involves Shrovetide Football, an early, unofficiated version of both association and rugby football. It was a mob game, first played in the town of Derby prior to Medieval times. From as early as the 12th century, it was known to have been played in Ashbourne. It was a chaotic and exuberant affair that involved populations from each town, often resulting in fatalities.  The goals were at Nuns Mill in the north of the town and the Gallows' Balk in the south of the town, Much of the action took place in the River Derwent or the Markeaton Brook. (you will need a map!). Nominally the players came from the All Saints' and St Peter's church parishes, but in practice the game was a free-for-all with as many as 1,000 players, probably from anywhere!! Who ever fancied a bundle!  A Frenchman who observed a match in 1829 wrote in horror, 'if Englishmen call this play, it would be impossible to say what they call fighting'.   

Shrovetide football is still an annual event in the town of Ashbourne. Since at least as early as 1840 'derby' has been used as a noun in English to denote any kind of sporting contest. So maybe the Ashover event might hold the origin???