This is the 5149th most frequent German word.
ass
"Ass" in German means "ace" (as in cards or someone exceptionally skilled).
Here, 'Ass' is used figuratively to denote high skill or expertise in an area.
Er ist ein Ass im Schach.
He is an ace at chess.
In this idiom, 'Ass' signifies a key advantage or trick used strategically.
Ein Ass aus dem Ärmel ziehen.
To pull an ace from the sleeve.
In this instance, 'Ass' literally refers to the playing card ranked as ace.