Can't help but love a name that gives an unpopular [gross understatement] group or individual the screamin' meemies.
The word, apparently brought into popular use by Australian Prime Minister Tony Abbott is Da'ish. When you read about it in the article linked to Tony Abbott the reason becomes clearer.
I just love it. Just makes me want to climb up and yell it over and over again from the rooftop. When transliterated from the Arabic the acronym reads ad-Dawlah al-Islāmīyah fil 'Irāq wa ash-Shām. The Da'ish, or as the collective terrorists murderers prefer to identify themselves; ISIS, ISIL, or now, just IS because the acronym has a nasty sound.
Probably POTUS Obama would not use the word Da'ish for fear of offending his Muslim brothers.