Actually, this happened to me regularly. None of the fixes above helped me. I used to know why it happened but I have forgotten. But I lived with it I think from one of the IOS 7 updates until IOS 8.1.3 or 8.1.4. I had a way to fix it. As you do this, note where each section was (3rd section down, etc). Trust me, it will help if you do not know more than one language. Go to settings>General>Language &Region>IPhone Language. Pick a language you are comfortable with (I used Japanese the firstt time and had to get Apple to walk me thru fixing it as nothing looked right. Now I stick to French as I studied that in school.). After you choose, it sets up the iPhone for that language. The icons will appear as they should. Now go back and do the same thing again, re choosing the language as English. You should be good to go. Until the next time you reboot your iPhone. Hth