After a horse, of course. In 1764, there was a solar eclipse on April Fool's Day - and that's when "Eclipse" was recorded as being born.
He raced for only 17 months and was retired - because he was so good he was ruining the betting industry.
He fetched 75 sterling as a yearling...and was bought by a farmer who, instead of gelding him, bet that he could be tamed by intensive training. He was untouchably fast - and a terror to handle. At the time, racehorses were run older than they are now - he made his debut at the age of 5 and won every race he was in...ignoring his jockeys the entire time (Not like they actually knew better).
He made $6 million from racing purses and stud fees, breeding over 300 mares. In fact, it's possible the horse box was invented for Eclipse (at that time, the stallion went to the mare). Over 90 percent of English Thoroughbreds trace to him.
In addition to the awards, Eclipse gave his name to a prestigious race, a racing magazine, the main building of the Royal Veterinary College and a slew of ships. (Not to mention the fact that "Eclipse" is still a common horse name, and not just amongst racehorses).
We don't know how Eclipse would have stacked up against, say, Secretariat or any other modern racehorse because they didn't have the best timing gear back then, but he was definitely insanely fast.