What's in a name? The politicians seem vexed about it. The Spectator sets out the position, for the record:
‘Isis’ is an acronym of Islamic State in Syria. ‘Isil’ – an acronym of Islamic State in the Levant. Isil is the better translation of the group’s Arabic name al-Dawla al-Islamiya fil-Iraq wa al-Sham – where ‘Sham’ represents greater Syria or ‘the Levant’ as we would say in English.
As for ‘Daesh’, it has the small propaganda advantage of reminding Arabic speakers of Daes (‘one who crushes something underfoot’) and Dahes (‘one who sows discord’). But beyond that childish word association it is no help at all, for ‘Daesh’ is just the Arabic abbreviation of al-Dawla al-Islamiya fil-Iraq wa al-Sham – or the Islamic State in Iraq and the Levant.