President Trump greets Sen. Luther Strange (R-Ala.) at a Sept. 22 rally in Huntsville, Ala., for the state's U.S. Senate race. (Brynn Anderson/AP)

On the occasions when President Trump’s rambling 90-minute speech in Huntsville, Ala., on Friday wandered back to its advertised subject, the campaign of Republican Sen. Luther Strange, the president tended to marvel less at the candidate’s politics than his height.

Six-foot-nine. “Big Luther,” as the president likes to call him. And before his speech ended, Trump appeared to have convinced himself he was the first person to ever use the nickname.

“I said, ‘That is the tallest human being I’ve ever seen!’ ” Trump said, recalling when he first met Strange before this year’s health-care battles. “That’s why I call him Big Luther. Everyone’s now calling him Big Luther.”

And sure enough, “Big Luther” is all over Strange’s campaign material as he lags behind his primary opponent, Roy Moore.

But others, including reporters and Strange himself, have been using the nickname for at least a decade, a point the president seemed unaware of as he continued his speech.

Trump digressed often from the virtues of Strange and into discussions of border walls and North Korea and football players. At one point, he said endorsing Strange might have been “a mistake” and promised to campaign for his primary opponent if the senator lost.

After half an hour or so, Trump returned enthusiastically to the origins of Strange’s nickname.

“Did people call you Big Luther before you met Trump?” he asked, looking out across the crowd.

“Yes!” someone yelled from the audience. But the president continued:

“You know, I brand people,” he said. “Some people I brand as this or that. We don’t need to go into it. …

“So, nobody ever called you Big Luther?”  Trump said. “I think it’s a great name. A guy 7 feet tall, what are you going to do? I could never call him Little Luther. I just saw him. I said, ‘He's Big Luther.’ And that’s cool.”

The White House didn’t immediately respond to The Washington Post about the conception of “Big Luther” or when Trump first called the senator such.

But it’s unclear why the two men would have crossed paths before 2006, when Trump was a New York real estate magnate and Strange was a Birmingham lawyer running to be Alabama’s lieutenant governor — known in local newspapers as “Big Luther.”

Strange spent much of his campaign funds that year on TV ads making light of his 81 inches, according to the Decatur Daily. The branding worked well enough that by October, one Helena, Ala., resident wrote a letter to the editor of the Birmingham News vowing to vote for “Big Luther Strange.”

But Strange lost to a Democrat, and next year, the Mobile Register reported that Big Luther was emailing supporters for help paying off “a small amount of debt.”

The name stuck, regardless. “Skinny-as-a-stick Big Luther,” wrote the Huntsville Times in 2009, as Strange ramped up his next political campaign.

He portrayed himself as a literal giant in 2010 when he ran to be the state’s attorney general. In a campaign ad, “Big Luther Strange Cleans Up Montgomery,” the candidate loomed dozens of feet tall above a crowd of cigar-smoking, martini-clinking political cronies, who a narrator explained were corrupting the state capital.

“It’s Big Luther!” they cried in unison as an enormous shoe touched down in Montgomery.

The suits fled, and a little boy then stood to greet Strange, who, by the way, did win that election — and was reelected in 2014, and then appointed to the U.S. Senate after Jeff Sessions vacated his seat to join Trump’s administration, styled all the while as “Big Luther.”

“Hear you’ll clean up Montgomery, Big Luther,” the little boy says in the 2010 ad, seven years before Trump took credit for the name.

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