Descriptive Naming, according to the manual, is a tricky subject. To really get at the essence of something, you can't just use names like 'this chair' or 'John Smith' such as you would use in ordinary conversation. This is especially true of people. You have to be able to describe a person uniquely, in terms of their own qualities and nature, in order to include them in a spell.

There is a worksheet provided for the naming of humans, in case he wants to try it on himself.