Sigh. Thanks. This is the second time I've been caught with an eggcorn[0]. First "windshield factor"[1], now "for prosperity sake". Looks like I might have the privilege of adding to their database myself this time...

We'll just keep this between you and me right?

[0] http://eggcorns.lascribe.net/

[1] http://eggcorns.lascribe.net/index.php?s=windshield