Look at the character:
乒 is
兵 (soldier) with the right leg cut off; its mate
乓 (pāng) has the left leg cut. The pair is a visual pun — 'soldier missing a leg' for the ping-pong sound. The sport
乒乓球 became China's
国球 (national ball) after the 1971 'ping-pong diplomacy' opened US-China relations.
