Let's go through the history of the letter S.
First the Acient Egyptians invented the letter S.
Our S, originally was the following symbol:
Back in time S meant sun.
After many years the Proto-Sinaitic people changed the symbol into this:
The letter S eventually evolutioned into our W in now a days by the Phoenicians:
The Paleo-Hebrew slightly did anything different, they just made the letter more abstract and thick:
The Aramics made it completely different:
The Greeks transformed it into this:
And that was the last evolution before our Modern European letter S: