For what it's worth, I got the idea after reading a brilliant (but cheap book) called "Winning through intimidation" by Robert Ringer.
It's nothing to do with beating people up. As Wynne says, it's about positioning yourself in such a way that people do not even dream of messing you about.
Ringer was a real estate broker in the USA. He used to put buyers and sellers of real estate together and collect a broker's fee. After getting ripped off a few times he totally revamped his marketing and the way he did business so that people looked upon him as the "main man". He was able to go into every deal in a real position of strength.
I guess it's one more step in being a professional.
People should not mess you about just because you clean carpets for a living.