One more flip could have given rise to the Epsom Bunbury, the Kentucky Bunbury, the Irish Bunbury and so on.
The tale goes that during the celebrations following the inaugural running of the Oaks Stakes at Epsom in 1779, a new race was proposed.
It would be named after the party's host, the 12th Earl of Derby, or one of the guests, Sir Charles Bunbury, depending on the toss.
Derby, whether by luck or subsequent negotiation, won the naming rights.
The first race, open to three-year-old colts and run over a mile (it's now one mile, four furlongs, roughly 2.4 kilometers) was held over the downs at Epsom, to the south of London, the following year and was won by Diomed, a colt owned by Bunbury.
Derby Day began as a Londoners' day out, where top-hat-and tail-wearing aristocrats mix with artisans of every persuasion.
It's now the blue riband of British racing and a global sporting and cultural spectacle.
This year's 238th edition is worth nearly £1 million ($1.3 million) to the winning connections.
"I've won the Breeders' Cup Classic and I've won the Dubai World Cup three times. They've got huge prize-money, but there's no occasion that gets to you like the Derby," said two-time champion Frankie Dettori
, who rides the favorite Cracksman for trainer John Gosden.
"It's stressful and nerve-racking. You feel the tension, but that's a good thing -- if you arrived at Epsom and you didn't feel it, that would mean the Derby didn't matter. And believe me, it does."
In the early years drinking, carousing, gambling, cockfighting, illegal bare-knuckle boxing matches and all manner of other activities ran alongside the racing.
In 1793, The Times newspaper reported
: "The road to Epsom was crowded with all descriptions of people hurrying to the races; some to plunder and some to be plundered. Horses, gigs, curricles, coaches, chaises, carts and pedestrians covered with dust crowded the Downs, the people running down and jostling each other as they met in contact."
Two years later the paper said the race attracted almost all of London's "vagabond gamblers."
Attendance swelled from around 8,000 in 1795 to 10 times that number in 1823, according to the official Epsom Derby website
The Derby is still the ultimate coming together of racing tribes, from the morning-suited upper echelons of society in the Queen's Stand -- the Queen herself has only missed two runnings since 1946 -- to the free open-air picnic area and fairgrounds of the Hill, controversially renamed Poundland Hill
this year after the budget retail chain became its first corporate sponsor.
Last year 154,00 spectators attended Epsom over the two-day festival, swigging 4,200 bottles of Champagne in the process.
The Derby's long history features the 1913 edition, dubbed the "Suffragette Derby," when women's rights campaigner Emily Davidson threw herself under the thundering hooves of King George V's horse Anmer and died four days later.
It took until 1996 for the first female jockey -- Alex Greaves -- to ride in the Derby.
Some of racing's most famous horses have cemented their legendary status with victory over the esteemed Epsom track, including Sea Bird, Nijinksy, Mill Reef and Nashwan.
One of the best known is Shergar, which won by a record 10 lengths in 1981, prompting the TV commentator to proclaim, "There's only one horse in it, you need a telescope to see the rest."
Less than two years later, Shergar was kidnapped from his Ballymany Stud in County Kildare, Ireland, and never seen again.
More recent champions have included Galileo (2001), sire of subsequent winners New Approach, Ruler Of The World and Australia, as well as the legendary Frankel. And then there's Workforce (2010), which holds the course record of two minutes 31.33 seconds under jockey Ryan Moore.
This year's field has swelled to a possible 20 runners after two horses -- winners of prominent trials -- were added as late entries at a cost of £85,000 each, taking the purse to £1.625 million ($2 million).
Italy's Dettori won the second of his two Derbys on Golden Horn in 2015, eight years after his first, which came at the 15th attempt.
"The Derby is the biggest race in the world, and consequently it is hard to win," said trainer Saeed bin Suroor,
whose only success came when he saddled Lammtarra to victory on his first attempt in 1995.
The tough course features a long uphill drag out of the starting gates, a left-hand bend around Tattenham Corner, a downhill gallop into the straight before an uphill finish.
"Epsom is the complete test of a horse," trainer Aiden O'Brien, who has saddled five Derby winners including Galileo, told BBC Sport.
"They need balance, speed and stamina. It's uphill, downhill, sideways. It's a very intense atmosphere."
The Derby. The Bunbury. What's in a name?