To many fans of Tottenham, the term "Yiddo" is a badge of honour, coined decades ago to mark out the football club's Jewish identity in the face of abuse and prejudice.
To the comedian and broadcaster David Baddiel, it is also a term with a deeply malign undertone, which offers an excuse to the supporters of other teams to launch into anti-Semitism.
Today, Baddiel and his brother Ivor will premiere a film, Y-Word, featuring Chelsea's Frank Lampard and Tottenham's Ledley King, which they hope will persuade the football world that it is not a term to be welcomed.
Since "Yid" and "Yiddo" chants are never heard in the final Match of the Day highlights edit, the Baddiels had to capture video phone footage and gather internet material. The film includes YouTube footage of fans singing: "Spurs are on their way to Auschwitz, Sieg Heil, Hitler's going to gas them again."
Baddiel was watching Chelsea play Aston Villa at Stamford Bridge two seasons ago when the news that Tottenham were losing at home to Hull City flashed on the big screen.
He and his brother, who is a writer, have become uncomfortably familiar during four decades of following Chelsea of "Yiddo" – a word with a complex, 700-year-old etymology which translates as "Jew" and has a self-deprecatory use for some. But what they heard that day took anti-Semitism to another level.
"People started up a triumphalist 'Yiddo' chant," Baddiel told The Independent yesterday. "Then a bloke behind us started singing 'Fuck the Yids.' Then he moved on to 'Fuck the Jews'. My brother, who is slightly harder than me, or maybe just a bit bigger, told him to shut up. The fan told my brother to fuck off. There was no violence, but the threat of it was very present. My brother sat down again. He said 'I think I'm going to cry'."
Chelsea offered to investigate but instead the film idea took root, developed with the Kick it Out organisation fighting against prejudice in football.
"Clubs are keen on one level to take on racism but also keen that their club should not be seen as racist," Baddiel said. Though the film's message is not directed at any one club, Tottenham have had some concern about the reaction of their own fans to a message not to chant the word. Chelsea also initially felt that they were being targeted.
"It is a difficult one, because this word is an historic call to arms, to deflect abuse," said Tottenham executive director Donna Cullen. "We would say the word is better not used."
Frank Lampard, the footballer, said: "For some reason some fans still shout the Y-word. Some might think it's just a bit of a laugh. But racist chanting is against the law. It's against the law to call someone the Y-word on the street."
The Y-Word can be seen at www.kickitout.org from noon today