The etymology of shit

At a friend's house I come across an interesting looking book called 'The Etymologicon' by Mark Forsyth.
I pick it up and sit in the terrace with it over a cuppa while my pal sleeps off last night's excesses. As I flick through the pages I'm immediately interested by the chapter concerning shit and fuck. Of course! I'm a boy and this behaviour seems to be de rigeur for boys who pick up books on language. "where's the naughty stuff?". I digress.
I was happily reading the etymology of the word shit when I stumble across an etymology for a Dutch word (scheiden, to separate). How so? From shit to separate?
Let's see...
Scitan (Old English for to shit)
Skit (proto-Germanic)
Skhei (proto Indo European for to separate)...which looks amazingly like the Dutch Scheiden: to separate!

Skhei also begat the word schism.
And of course shit and scheisse.
Charming, I know.