This card's name may refer to a term used in baseball. Accordingly, an "ace" is the best starting pitcher on a team and nearly always the first pitcher in the team's starting rotation. Barring injury or exceptional circumstances, an ace typically starts on Opening Day. In addition, aces are usually preferred to start crucial playoff games, sometimes on three days rest.
This monster's artwork depicts its effect in action: when the opponent 's card is activated, this monster can throw the energy ball to the card and destroy it.
Also, the "Once per turn, during your opponent's turn" part could be a reference to baseball's rules: during the batter's turn (opponent's turn), the pitcher can only throw one ball at a time.