"Flush" in the poker context has more to do with definitions 1 (Abundantly full. In later use chiefly of a stream, etc.: Full to overflowing, swollen, in flood.

"Flush" in the poker context has more to do with definitions 1 (Abundantly full. In later use chiefly of a stream, etc.: Full to overflowing, swollen, in flood.) and 3 (Plentifully supplied (esp. with money).) rather than 5 (Even, level, in the same plane with / Even or level with the adjacent surface.). To be "flush with money" is to have a lot of money---in poker, to be flush with hearts is to have 5 hearts. http://www.oed.com/view/Entry/72182?rskey=4UKORw&result=4&isAdvanced=false#eid http://www.oed.com/view/Entry/72182?rskey=4UKORw&result=4&is...