There are valid U.S. trademark registrations for the mark PING PONG covering, uh, table tennis stuff, stating a date of first use of 1902.  The original registrant was Parker Brothers.

History of Ping Pong here.

Cats playing ping pong from here.

UPDATE:  A loyal Trademark Blog reader emails me to advise that (1) the owner of PING PONG trademark enforces its rights; and (2) it backs it up with dictionary definitions defining PING PONG as a trademark for table tennis (a fact I confirmed by looking at my Webster’s.

Etymology Question: Does the term ‘to ping’ as in to send something over a network to test it (and now, to follow up with someone – “If he doesn’t answer by tomorrow, ping him”) derive from PING PONG or from the meaning of ping as in small metallic noise (“the engine pinged”).