Owner David Evans -- who's also the horse trainer -- entered the horse to run at the Wolverhampton Racecourse in the U.K. on Saturday ... and as soon as "JB" hit the track, there was outrage on social media.

FYI, the term "JB" is a super racist term for Black people that racists have been using for decades.

But, Evans insists racism played no role in how the horse got its name -- instead, he claims his daughter innocently came up with the moniker, inspired by a video game.

"David's daughter gave us the horse and there's a computer game called Jungle Bunny Run," his wife Emma told The Daily Mail.

"I just thought, that'll do. I had no idea. It was completely innocent and that is the gospel truth. None of the staff said anything, nobody else said anything and I'm totally flabbergasted."

The British Horseracing Authority is PISSED the name wasn't flagged before Saturday's race -- and claims it's now taking proper action.

"This name is deeply offensive and should not have been permitted," the BHA said on Twitter.

The BHA later issued a 2nd statement saying, "We have taken steps to ensure the horse was renamed immediately. It is now called Jungle Bells. This will be reflected in records of the race result and horse form."

"We are deeply concerned as to how this happened and are reviewing the processes for approving the names of racehorses."