What is the origin of on and off power switch symbol?
I'm pretty sure it comes from the binary 1 (on) and 0 (off) 

It's an IEC standard symbol, the on symbol is IEC-5007 and the off symbol is IEC-5008 

The full standard document they come from is IEC 60417, which you have to pay for, but here is a small reference document with just the power symbols reproduced.