Barring the door is an expression based on the old practise of using an iron bar to secure the door of one's home from the outside. The bar was hinged on one doorpost and could be secured into a latch on the opposite door post. Hence "barring the door."
Katie is just a silly name used for no good reason at all.
Well see, I thought the name meant something. Cuz I know what it means to bar the door, I just thought there was something more to it that had to do with some girl named Katie.
thats my name. and its also the name of the lady at the temp agency. we keep calling eachother and saying "can i speak to katie, katie calling" n stuff