What's in a name?

So the PM has determined that we should call our enemy in Syria Daesh - which he pronounces Die-esh.  The Americans tend to pronounce it "Dash" - but then, they have a habit of always coming up with their own pronunciations  - Eye-raq for Iraq and so on.  But apart from that, just what should we call this would-be Middle-Eastern caliphate?  It started out life as the Islamic State, then it became the "so-called" Islamic Sate, then ISIS or ISIL and now apparently to be on-song we must go with Daesh.  Does it matter?  Apparently the terrorists themselves don't like the name, which is perhaps why we've decided to use it, but what we call them is surely a side-issue.  I am reminded of a John Le Carré story (was it "A Little Town In Germany"?) where more time was spent on discussing what code-name a spy operation should be given rather than how it should be run.  Now we've decided to go in, let's just get on with it, whatever we call them.