Like any other religious or ethnic group, there are insults specific to the Jewish communty, some of greater or lesser intensity. But “kapo” belongs to a special category of awfulness.
The term is viewed with disgust by many Jews, most of whom would never choose to use it.
Using the most painful episode of Jewish history, it accuses Jews today of actively betraying their fellow Jews by working for their oppressors.
"Kapos" were created by the SS, the Nazi troops responsible for murdering most Jews killed in the Holocaust.
The SS tormented those it chose to keep alive in its camps for slave labour.
The Nazis would select some prisoners in the camps and give them preferential treatment, including extra food and no hard labour, in return for helping keep other prisoners in line.
These "kapos" worked as overseers, beating and sometimes even killing their fellow prisoners.
Although there were some examples of kapos trying to help those under their authority, many were known for their harsh, cruel behavior, in a desperate attempt to ingratiate themselves with their captors.
A kapo who was deemed not harsh enough could be “demoted” back to being an ordinary prisoner.
The tenuous nature of the hierarchy, where kapos sat between the SS and other prisoners, was deliberate. In 1944, Heinrich Himmler, head of the SS, said: “The moment he becomes a kapo, he no longer sleeps with them.
"He is held accountable for the performance of the work, that they are clean, that the beds are well-built...
"So, he must drive his men. The moment we become dissatisfied with him, he is no longer a kapo, he's back to sleeping with his men. And he knows that he will be beaten to death by them the first night.”
in 1950, Israel passed the Nazi and Nazi Collaborators Law, which led to around 40 trials over the next 15 years, most of people accused of being kapos.
One of the most common uses of the slur within the Jewish community comes from those on the right towards those they perceive as being too sympathetic towards the Palestinians.
Jews who describe themselves - or even are just perceived as being - anti-Israel, anti-Zionist or anti-Israel's occupation of the West Bank are branded "kapos" by some right-wing Jews as supporting those who seek the destruction of Israel.
"Kapo" was a common insult against against young left-wing British Jews who took part in last year’s “Kaddish for Gaza”, where they recited the Jewish mourner’s prayer for Palestinians killed by the IDF in clashes on the Gaza border.
In March this year, Shraga Stern, strictly orthodox anti-LGBT education activist, used the slur against strictly orthodox Rabbi Avraham Pinter.
Mr Stern claimed the rabbi was helping Ofsted as it seeks to enforces making the teaching of LGBT issues compulsory, which Mr Stern claimed would pose a mortal threat to children's Judaism.
There are also, however, an increasing number of examples of left-wing Jews using the slur against right-wing Jews, particularly supporters of Donald Trump.
A Jewish anti-Zionist cartoonist Eli Valley is known for his attempts to “take ownership” of the term, “to seize the tool of excommunication and start using it” – by which he means using it to describe and depict right-wing Jews.
Social media suggest other Jews on the far-left, particularly in America, have begun to follow his example.