In its renewed declaration of war against ISIS, the hacker group Anonymous referred to the Islamic militants as "Daesh." It's a term that's also been used by President Obama and French President François Hollande following Friday's deadly terrorist attacks in Paris.
"France will be pitiless concerning the barbarity of Daesh," Hollande said, even as declared a state of emergency and ordered 1,500 extra troops to guard buildings and schools in the wake of the attacks.
What is Daesh?
The group known as ISIS, or the Islamic State of Iraq and Syria, goes by several other names, including ISIL, or Islamic State of Iraq and Levant (a reference to a geographic region including Egypt, Syria and Turkey) and the Islamic State.
Obama, Hollande and U.S. Secretary of State John Kerry, as well as other world leaders, have started referring to the group as "Daesh." The word, according to Arabic translator Alice Guthrie, Daesh is a transliteration of the Arabic acronym of the same words that make up ISIS in English.
The way the acronym sounds when pronounced references someone who is a tyrant, or a murdering fundamentalist who claims to be Islamic. It can also sound like the Arabic phrase for "to trample or stamp down."
So why does ISIS hate it?
The acronym/word was used by ISIS for a certain period of time but is now banned by ISIS, which has threatened to cut the tongue out of people who use the word. Syrian fighters battling ISIS have also adopted the word.
Evan Kohlmann, a national security analyst, told NBC News the word is similar to referring to a German person as a "Hun."
"They hear it, quite rightly, as a challenge to their legitimacy: a dismissal of their aspirations to define Islamic practice, to be 'a state for all Muslims' and crucially as a refusal to acknowledge and address them as such," Kohlmann said.
Guthrie explains it this way:
"So the insult picked up on by Daesh is not just that the name makes them sound little, silly, and powerless, but that it implies they are monsters, and that they are made-up," she said.
As far back as early 2014, advisors were recommending the use of the word Daesh.
"Changing what the United States calls this band of militants is not going to make them go away. Yet we also know from over a decade of war that military tactics do not stamp out extremism either. As the prominent Muslim sheikh Abdullah bin Bayyah recently said after issuing a fatwa against the group, "The problem is that even if you defeat these ideas militarily by killing people, if you don't defeat the ideas intellectually, then the ideas will reemerge," Zeba Khan wrote for the Boston Globe in 2014.