How Did My Boy Jack Get His Name? This Kentucky Derby Horse Is Apparently Named After A Real Person

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When the 144th annual Kentucky Derby kicks off in Louisville, Kentucky, on Saturday the stands will likely erupt in shouts of "go, Free Drop Billy," "get 'em, Lone Sailor," and "come on, My Boy Jack" as the horses thunder around the track. With a reputation for running well on muddy tracks, My Boy Jack has quickly become a betting favorite as rain at Churchill Downs has muddied the track. But how did My Boy Jack get his name? Rumor has it, his namesake is human.

Although My Boy Jack is also the name of a rather famous poem written in 1916 by Rudyard Kipling after his son was presumed to have been killed in action at the Battle of Loos during World War I, the poem — and subsequent book and film of the same name — don't appear to be the inspiration behind this racehorse's name. According to Bradley Weisbord, founder of the racehorse bloodstock agency BSW Bloodstock, which counts some of My Boy Jack's owners as clients, My Boy Jack's namesake is a human boy named, you guessed it, Jack.

My Boy Jack was reportedly named for the son of Sol Kumin's partner in Monomoy Stables, Weisbord revealed on Twitter earlier this month when he posted a picture of My Boy Jack's namesake at Churchill Downs. "Don't tell his teachers why he missed school today," Weisbord wrote. Oops, the secret might be out.

While a number of this year's Kentucky Derby entries may appear to have names that border more on the bizarre and imaginative side of things, there are rules for naming racehorses. The Jockey Club, one of horse racing's governing bodies, dictates that a racehorse's name can be up to 18 characters long. Although it's worth noting that both spaces and punctuation count as characters.

Racehorses can't share names or have names the Jockey Club deems to be too similar, meaning owners must find clever ways of combining or playing off the names of established racehorses should they decide they want to name their horse after its pedigree. Other popular ways owners name racehorses include drawing inspiration from the locations, pastimes, things, or people that they love, according to NBC.

In fact, it's not uncommon to have a horse named after a real person — dead or alive. But there are some extra rules should an owner decide they want to name their racehorse after a person. "One of the naming rules is that written permission is needed to name a Thoroughbred after a living person," Jockey Club registrar Rick Bailey told NBC.

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While My Man Jack appears to have been named for the son of Kumin's partner, Kumin has admitted to naming a horse after his own son. Kumin told racehorse news outlet Blood Horse that he'd named My Man Sam, who ran in the 2016 Kentucky Derby, after his own son.

Although Justify was the morning-line favorite, support for My Boy Jack began building among betters after some serious rain muddied the track. According to the Baltimore Sun, My Boy Jack rose from a 30-1 betting choice to a 5-1 choice as spectators began to consider which horses would run well in mud. My Boy Jack pulled away from the pack to easily win the Southwest Stakes earlier this year despite the muddy track.

And if My Boy Jack does win Saturday, expect it to be a crowded winner's circle. Kumin and his partner own My Man Jack in partnership with Kirk Godby of Don't Tell My Wife Stables and Terrance Finley of West Point Thoroughbreds, according to the Kentucky Derby's official website. Godby told the Los Angeles Times that My Boy Jack had 66 people rooting him on at Saturday's Kentucky Derby.