Similar to jew and possibly due to the common suffix of -stein in Jewish names.
You steiners better come up with that 20 bucks you owe me.
"I gave her a 10, but she gave me back change for a 20. Stein!"
"Charles Shaw is only $2 a bottle at Trader Joe's. It's a total stein."
"He never brings anything to a party--what a stein."