Why Tom is 'Tom 7'
As it turns out, my name really is Thomas Walter Murphy VII. My father is the 6th, his father the 5th, etc. When I was growing up, we'd get phone calls for "Tom", and due to the ambiguity, we'd have to ask, "big Tom, or little Tom?". I eventually got sick of being "little Tom", and "Tom Junior" isn't really accurate, so it became "Tom 7".
Now that I'm in Pittsburgh, where the mayor's name was also Tom Murphy (for like 12 years, at least), "Tom 7" helps keep me straight from him and all the bajillions of other Tom Murphys around.
And now you know!