I always thought GO stood for General Order. Refers to the order under which the person's commanding officer committed his unit to a certain battle or campaign, or the order to troops for a particular course of action being undertaken.If that's true here, the 33 and 40 are the General Order numbers.
There should be an index to the Army General Orders for WWII, for this particular combat division. I have seen them online for WWII, for the 99th and one GO 33 online which refers to an order for a unit in Korea to fly a flag at half staff, to honor a former commander.
Maybe someone out there has the index for this unit already and can be more specific. Hope this helped.