The House of Representatives on Tuesday invoked an ancient procedure to strike from the record offensive words about the president that were uttered on the floor by one if its members.

But that offender wasn't the one who called President Donald Trump's tweets "racist."

Since its first days over two centuries ago, the U.S. House has had rules against impugning the motives — not the policies — of other lawmakers, the Senate, or the president. Remarks "shall be confined to the question under debate, avoiding personality."

It was Rep. Eric Swalwell (D-Calif.) who crossed this line Tuesday. He said of Trump, "Calling African countries shithole countries is racist, and telling four members of this body to go home is racist."

Oddly, it was not his allegation of racism that was stricken from the record; it was the profanity in the middle of the sentence. After a rebuke, Swalwell relented. "I will withdraw an offensive word."

Meanwhile, the House raged over a resolution condemning Trump's tweets. Republicans attempted to use the same procedure — called "words taken down" — against House Speaker Nancy Pelosi for saying members should all "join us in condemning the president's racist tweets." The Democratic majority ultimately voted that Pelosi's statement did not violate House rules on proper debate, leading Minority Leader Kevin McCarthy (R-Calif.) to rise and somberly declare: "Today is a day that historians will write about."

McCarthy may be right, but on the bright side, nobody will remember that historians wrote about it.

In October 1993, a prior Republican minority leader, Rep. Robert Michel of Illinois, published for his colleagues a detailed history of "words taken down," the procedure in the House for striking from the record offensive words spoken by a lawmaker during House debate. When Michel died in 2017, most obituaries made note of his reputation as a champion of civility in Congress.

"The House, with its ethnic and cultural diversity, debates issues with a passion not seen in the other body," Michel warned. "Unlike the Senate, the House speaks directly to 'the people.' And with many very controversial issues in our society today, including abortion, the capital gains tax cut, the economy, health care and others, the rhetoric can and does get very heated."

Michel warned his colleagues that "With frayed emotions and partisan sniping, the temptation to launch into personal attacks is very strong indeed."

Michel's report documented dozens upon dozens of cases throughout the history of the House that set precedent for what lawmakers can and cannot say on the House floor. As he said in his cover letter, "You can ask if there are any 'paid agents of Hitler' on the Congressional payroll, but you can't call a member of Congress a 'pinko.'" In 1945, a member of Congress was warned for referring to another member as the "Jewish gentleman from New York," instead of simply "the gentleman" — but his words were not stricken.

Michel notes that bigotry has been debated before. In 1967, Rep. Felix Hebert (D-La.) said of another lawmaker: "His conclusions have already been reached. They are prejudicial and bigoted." Then-Speaker of the House John W. McCormack (D-Mass.) ruled the words out of order, saying, "The Chair is of the opinion that the particular use of the word 'bigoted' is not consistent with the rules of the House." One presumes McCormack would have a dim view of "racist" as well.

The report is a fun read and a window into the shifting outrages of Congressional history, but it is almost impossible to find. Neither the House Library nor the Library of Congress has a copy. WGBH News obtained a copy from the folks who manage the Robert H. Michel papers at The Dirksen Congressional Center in Pekin, Ill.

Michel wasn't the last to try to record this history of offensive congressional speech.

In 1999, the Congressional Research Service had a go of it, publishing a report that included a section about what lawmakers can and cannot say about the president. In general, the report concluded, criticizing presidential policy is in bounds; criticizing the president personally is out of bounds. "References to the President that have been ruled unparliamentary include calling the president a 'liar,' attributing 'hypocrisy' to him, accusing him of 'demagoguery' and alluding to alleged personal misconduct or a 'propensity for unethical behavior' on the president's part."

CRS also notes that "Members may not engage in personal abuse, innuendo, or ridicule of the President."

Of course, these restrictions apply only to debate on the House floor, not Twitter.

This article has been updated to show the correct spelling of Rep. Eric Swalwell's last name. It is Swalwell, not Swalwel.