American columnist and the daughter of late Sen. John McCain (R-AZ), Meghan McCain’s tweet sent her followers scrambling to find out the meaning of an archaic saying, Tuesday.

“As my father always used to say to me - Illegitimi non carborundum,” Meghan wrote in a short tweet hours after President Donald Trump launched a fresh round of attacks on her father, who died in 2018 of brain cancer.

According to Urban Dictionary, “Illegitimi non carborundum” is a mock Latin term, when translated read - “Don't let the bastards grind you down.” To break it down, the Latin word “illegitimatus” meant “bastard” and the term “carborundum” belonged to an old brand of abrasives.

The term could be traced back to World War II when lexicographer Eric Partridge attributed it to British army intelligence. It was popularized in the U.S. by 1964 presidential candidate Barry Goldwater.

The term also appears in the first verse of a fight song of the Harvard University Band:

“Illegitimum non carborundum;

Domine salvum fac.

Illegitimum non carborundum;

Domine salvum fac.

Gaudeamus igitur!

Veritas non sequitur?

Illegitimum non carborundum—ipso facto!”

Trump’s latest attack on John came in reply to a reporter’s question during a press conference alongside the president of Brazil, who was at the White House for an official visit, Tuesday. When a journalist asked the president why he found new ways to defame the late Arizona senator, he said he was “never a fan” of Republican lawmaker “and I never will be.”

The POTUS further elaborated on his hate for the senator, saying it was John’s historic vote against the Republican measure to repeal the Affordable Care Act in 2017 that started the feud between them.

“He campaigned on repealing and replacing Obamacare for years, and then he got to a vote and he said thumbs down,” Trump said. “Our country would have saved a trillion dollars and we would have had great health care.”

Over the weekend, Trump rebuked John for the latter’s alleged ties to the controversial Russia dossier:

Meghan fired back almost immediately with a scathing reply. "No one will ever love you the way they loved my father," she tweeted Saturday. "I wish I had been given more Saturday's [sic] with him. Maybe spend yours with your family instead of on twitter obsessing over mine?"

A number of the Republican senators also had Meghan’s back as they defended her father against the president’s attacks.

“As to @SenJohnMcCain and his devotion to his country:  He stepped forward to risk his life for his country, served honorably under difficult circumstances, and was one of the most consequential senators in the history of the body,” Sen. Lindsey Graham (R-SC) wrote in a couple of tweets. “Nothing about his service will ever be changed or diminished.”

Sen. Mitt Romney (R-UT) tweeted: “I can’t understand why the President would, once again, disparage a man as exemplary as my friend John McCain: heroic, courageous, patriotic, honorable, self-effacing, self-sacrificing, empathetic, and driven by duty to family, country, and God.”

Cindy McCain, Meghan’s mother, took to Twitter, Tuesday, to share a vile and abusive note sent to her by a hater, following the president’s remarks. In the note, a woman had called her a “c--t” adding, “Your husband was a traitorous piece of warmongering s--t and I’m glad he’s dead.”