Reviving a derogatory nickname he used throughout his presidential campaign, President Donald Trump referred to U.S. Sen. Elizabeth Warren as "Pocahontas" during a speech before the National Rifle Association's convention on Friday.

Trump, the first sitting president to address the group since Ronald Reagan, began his speech by reminding those in attendance that he was the only candidate to address the NRA during the last presidential election cycle. But he said ahead of the 2020 election, he expects more candidates to do the same.

"I have a feeling in the next election you're going to be swamped with candidates," he said. "But you're not going to be wasting your time. You'll have plenty of Democrats coming over and you're going to say, 'No sir, no thank you. No ma'am' - perhaps ma'am. It may be Pocahontas, remember that. And she's not big for the NRA, that I can tell you."

While he was running for president, Trump repeatedly denigrated the Democratic Massachusetts senator as "Pocahontas," a reference to claims she has made about being part Native American. The nickname first surfaced during Warren's run for Senate in 2012 against incumbent Scott Brown.

During that campaign, law school directories from the Association of American Law Schools from 1986 to 1995 surfaced that put Warren on the association's list of "minority law teachers'" when she was teaching at the University of Texas and the University of Pennsylvania. Warren said she listed herself with Native American heritage because she hoped to meet people with similar roots.

In a 2012 interview with The Associated Press, Warren said she and her brothers were told of the family's heritage by their parents, the late Don and Pauline Herring.

Trump has used the "Pocahontas" reference on several occasions this year, including a February meeting with Republican and Democratic senators.

Sen. Al Franken (D-MN) criticized the reference at the time, calling it "racist" and "completely unacceptable." Native American leaders have called Trump's attacks on Warren offensive and distasteful.

Trump's remarks on Friday — this time with the presidential seal affixed to his lectern — drew a similar response from some on Twitter.