Six Degrees of Separation

Apparently, any one of us is separated from any other person by only six degrees of separation. I don't know where I had first heard of that. Perhaps in a movie. However, when one thinks of separation, and about intimacy and all nuances in-between, one gets a rather voluminous tome. I saw this girl a couple of days ago and gave her a ride. The strangest thing is that I don't know her name. I also learnt that she is defending her thesis in a couple of days and then she will vanish, like a puff of smoke, into oblivion. Then there are others, of whom I know names. And I also know that some among those like adopting children, while others who want children, and still others who think children are cute to look at while asleep, while the greatest menace while awake. And then there are others of whom, although I know names, knowing where we stand is the most difficult thing ever. Degrees of separation they say! Yeah. Degrees of separation... I concur. But six? Where did one come up with that ?