What's In A Name?

It's amazing really, how wrong people can get a four letter name. The variations I get at work are bizarre, considering that these are in emails people are replying to, from me, that have Izzy spelled out at the bottom. They must have read it to know the name to reply to, so why do I get, in the last working day, variously Issy, Issey, Issie, and best of all, just now, Liz.