The term ‘Daesh‘ is an abbreviation of the arabic ‘al-Dowla al-Islaamiyya fii-il-Iraq wa-ash-Shaam’ (which translates to ‘The Islamic State of Iraq and Syria’ – ISIS) but the terror group hate the name ‘Daesh’ and threaten to cut out tongues for using the acronym.
They don’t like the name Daesh because ‘Islamic State’ sounds more legitimate, plus ‘daesh‘ sounds like various words with negative connotations in Arabic.