Sen. Elizabeth Warren (D-Mass.) is very upset that President Donald Trump referred to her as “Pocahontas” — so upset, in fact, that she’s observing the time-honored tradition of politicians who have been deeply, personally offended: She’s raising money off of the event.

What’s the background here?

According to The Hill, Warren sent out a fundraising email in response to an apparent jab from President Donald Trump during a ceremony Monday that honored surviving Navajo “code talker” veterans.

During the ceremony, Trump remarked, “Although, we have a representative in Congress who has been here a long time … longer than you — they call her 'Pocahontas.' But you know what, I like you. You are special people.”

The dig was an obvious reference to Warren, who Trump has frequently referred to as “Pocahontas” in speeches and tweets.

Why does Trump call Warren 'Pocahontas'?

Conservative activists first began referring to Warren as “Fauxcahontas” during her successful 2012 Senate campaign against Republican incumbent Sen. Scott Brown.

The nickname referred to Warren being erroneously listed as a “minority” professor in her Harvard Law School bio because of her “Native American” heritage.

These revelations led to allegations that Warren exaggerated the extent of her Native American heritage in order to improve her job prospects at Harvard.

Warren’s explanation for the listing, which was widely panned, was that she “self-identified” as Native American in order to increase her opportunities to meet others of similar background.

The controversy led Massachusetts Republican activists to frequently taunt Warren as “Fauxcahontas” to criticize her for faking or exaggerating a Native American heritage.

Trump’s habit of calling Warren “Pocahontas” is almost certainly a reference to this controversy, although it is not clear how or why Trump decided to change the taunt from “Fauxcahontas” to “Pocahontas.”

What did Warren’s fundraising pitch say?

According to The Hill, Warren’s email accused Trump of making a “racist slur” against her and asked for donations to support Warren’s political efforts.

"You might have heard that Donald Trump likes to call me 'Pocohontas.' He does it on Twitter, at rallies, and even in official White House meetings," an email from the Massachusetts Democrat reportedly read.

“Let’s show Donald Trump that we’re sick of his racist slurs by getting to work to fight his agenda. Donald Trump can keep attacking my family — but I am going to keep fighting for yours,” she added.

The White House has defended the president’s remarks, denying that the comments are a racial slur.