Etymology: Japanese, from tsu harbor + nami wave

Well a "harbor" is certainly where the impact of the 'great wave' is felt, Vernon, but I don't think that takes anything away from Of Troy's discussion, do you?

BTW apparently the 'harbor wave' which hit Indonesia was only a meter high* [compared to several times that height elswhere including Thailand] so a tsunami does not have to be a 'great wave' to have great and terrible impact.

* This was reported by the Jakarta Post but it appears to be an understatment because a wave of 2.6 meters was recorded as far away as Mexico.

"Waves of up to 10 meters in height struck Northern Sumatra, the Nicobar and Andaman Islands, Thailand, Shri Lanka, India, the Maldives, Somalia, Kenya and the islands off the African coast. The tsunami was recorded by tide gauge stations not only in the Indian Ocean, but in the Pacific as well. In Manzanillo in Mexico, the tide gauge recorded a wave of 2.6 meters."

http://www.drgeorgepc.com/Tsunami2004Indonesia.html