In the spirit of the cross, Christians around the world are now adopting the Arabic letter “nun,” the rough equivalent of the Roman alphabet’s letter “n,” as their icon on Facebook and Twitter. Some are painting or posting it on their doors. Protesters from Baghdad to Paris have marched with signs displaying the “nun” (pronounced noon).

Nun is the first letter of the word Nazarene, a rather dismissive way of referring to Christians in Arabic. Fighters for the Islamic State in Iraq and Syria (ISIS) spray painted doors and walls of Christian homes, businesses and churches in Mosul, Iraq’s second largest city, with the letter before issuing an ultimatum to the city’s Christian population.

Mosul Christians had until midday July 19 to convert to Islam, pay a special tax (jizya) or be killed. In the euphemistic language of the threatening letter sent to Mosul’s Christians, leaders of ISIS said, “There will be a sword between you and us.”

The Christians knew exactly what that meant and got out of town. The option of paying the jizya was withdrawn at the deadline.

The nun will be prominently displayed at a Toronto protest against persecution of Iraqi Christians planned for Aug. 10. Fr. Niaz Toma of the Chaldean rite parish of St. Thomas in Hamilton has been organizing Catholic participation in the 3:30 p.m. march from Bay and Front Streets to Queen’s Park.

The Archdiocese of Toronto has urged the federal government to bring full diplomatic pressure to bear to protect Christians in Iraq, said spokesman Neil McCarthy.

A prayer vigil for Iraq’s Christian minority is being planned for St. Paul’s Basilica in Toronto Sept. 7.

ISIS also threatened the Shiite Muslim minority in Mosul, marking Shiite doors with the letter “ra” for “rejectionist.” The Sunni Muslim fundamentalists behind ISIS and its self-proclaimed caliphate regard Shiite Muslims as apostates and heretics.

Not only Christian Iraqis but many Muslims in Baghdad gathered outside a church in Baghdad to protest ISIS rule in northern Iraq, holding signs displaying the letter nun, the Al Arabya News agency reported. In Paris 100 protesters gathered in front of the French National Assembly with nun signs to show support for Iraqi Christians.

In Canada and around the world Christians have turned to social media. Calgary mother and freelance writer Sara Francis is one of thousands who have adopted the nun for their Twitter and Facebook icons.

“I certainly don’t think ISIS will care if a million people change their profile pictures to condemn their actions,” Francis told The Catholic Register. “On the one hand it seems trite to sit in my safe, peaceful, suburban home and think changing my profile picture means anything while my Christian brothers and sisters are being uprooted, persecuted, even killed. On the other hand, maybe changing my profile picture will raise some kind of awareness among my friends and then their friends.”

Francis has also used Facebook to promote a day of fasting and prayer for Iraqi Christians.

“This social media thing is actually helping me not to feel powerless and tune out. People are reading my posts. I’ve had people comment who I haven’t spoken to in years… Even if my profile picture doesn’t make a difference to ISIS or the government or the media or even my friends, it has made a difference to me. It’s a daily reminder every time I log onto Facebook to keep praying for the people of Iraq.”

McGill University professor of Christian thought Douglas Farrow has taken the nun beyond his social media icon. He has also posted it on his front door.

“When one become s a Christian, a Nazarene, one is marked with the sign of the cross. The marking of Christian dwellings with a threatening nun — like the marking of Jewish dwellings with the Star of David — is a way of recognizing that, and of asking Christians whether they really mean to be followers of Jesus,” Farrow said.

Like Francis, Farrow is wary of engaging in empty and self-aggrandizing gestures.

“If all we’ve done is made ourselves feel good by having complained about (ISIS terrorism and oppression ) , then we’ve done nothing useful and perhaps even deceived ourselves,” he said. “Unless it is accompanied by other forms of direct action — prayer, fasting, giving, etc. — of course it doesn’t mean anything.”

The Christian talent for transforming the violence of the cross into a symbol of love isn’t just a rhetorical trick. It is part of Christian DNA, inherited from Jesus, said Jesuit theology professor Fr. Gilles Mongeau. Mongeau has also adopted the nun on Facebook.

“The chutzpah of Christians is to take the original symbol of oppression and celebrate it as an expression of love. They could very well ignore or forget the original violence that was transformed and overcome by the love, but instead they face the violence and let it be exposed for what it is, even as they celebrate that it has been overcome by love,” Mongeau wrote in an e-mail. “So the nun is paradoxically made into an occasion for me to say out loud ‘I love you’ and that love is stronger than death and violence. And it pushes me to do something more for justice, even if it cannot go much further than prayer and fasting — which is still a lot.”

Christians “need to conceive of themselves as belonging to an exiled people. In that sense, I think it’s useful,” said Farrow.

Muslims who have adopted the nun on Facebook and Twitter are trying to reclaim their religion from people who have turned it into a justification for violence.

“Islam is about mercy. Muslims have always lived peacefully with all religions. This is what God commands us,” Iraqi medical student Rawan Alrawi told The Catholic Register from Jordan where he studies.

Like other Iraqi Muslims, Alrawi has made the nun into his Twitter icon.

“This is not going to change (ISIS’) mind, because they don’t even have brains to think. But it’s to show our unity… We are all ‘nun.’ There’s no difference between us,” he said.

Iraqi Christians have been part of Iraq for 2,000 years “and no one has the right to make them leave their land and homes,” said Alrawi. “This is not Islam.”

“Clearly the self-appointed caliph and his military commanders don’t care what my Facebook image happens to be,” wrote retired Iraqi teacher Kawthar Abdullah from Qatar. “Regardless of what religious group or nonreligious group we each identify ourselves with, it is our obligation as human beings to support and protect each other… The nun solidarity movement must be global and adopted by all. It will have more effect if non-Christians join.”

As a Shia Muslim, Abdullah is horrified both by the ISIS demand for forced conversions and the assault on Muslim heritage by Wahabi-sect ISIS fighters. ISIS fighters have blown up mosques and imposed their version of Islam on innocent Iraqi Muslims. Their effort to push Christians out of their caliphate is just another example of how little they understand Islam, said Abdullah.

“Forced conversions are null and void and nobody has the right to force Christians or any other group to leave their home country according to Islamic teachings,” he said.

Jesuit Brother Dan Leckman worries about the nun movement being taken up by the sort of Christians who would “come dangerously close to reducing Islam to a cult of violent radicals.” But he has adopted the nun on Facebook in the hope that any expression of solidarity must lead to peace.

“I realized the violence is real, but it tells me nothing about Islam — that what defines Islam is its holy relationship to God, not its hate of others,” Leckman said.

Working in a retreat house in Montreal, Leckman knows there’s not much he can do to counter the violence in Iraq.

“I’m not even sure what change we can hope for in this situation, so maybe this is the only gesture we can do,” he said.