See Islamic State
Daesh is play on words: Da’esh is an acronym for the Arabic al-Dawlah al-Islamīyah fī al-ʻIrāq wa-al-Shām (Islamic State of Iraq and al-Sham), used because it is similar to the verb daes, which means to crush something underfoot, or dāhis, one who sows discord.
Daesh has been adopted by some western politicians in an attempt to undermine the group’s credibility.
Use Islamic State.