"Phycoin" rolls off the tongue better than "Physcoin". That just sounds like fizz coin.
And the more i say it out loud, the more i like it.....
"Ere Dave, you gotta couple of Phys, mate?" or "Thank you sir, thats 2 Physcoin change. Have a nice day".
Edit: How about 'Crypts' ?
Crypts or cryptcoin.