O.K. then, here goes, but it is unlike Trevor. I hope he has not taken offence, as he makes some excellent contributions to this site - and, anyway, I bet I am older than he.
However, I think you are right with Past and, if you are past mixed class you would be rich. Put them together and you have PASTRICH. There is a well known Dr. Howard Pastrich. Google him to confirm.
Best Wishes,
Colin