|Woodblock print of Tsunami by Hokusai|
Here's a wiki about "tsunami etymology," including the word for it in a few other languages. A tsunami-like wave was described by the Greek historian Thucydides (426 B.C.), and by the Roman historian Ammianus Marcellinus when he described the sequence of events that destroyed Alexandria in 365 A.D., but as far as I can tell they did not appropriate a special word for the phenomenon in either Greek or Latin. The word "tsunami" was brought into English use about 100 years ago when an earthquake on June 15, 1896 caused a tsunami to hit Sanriku, very near the site of the current devastation. There was a report in National Geographic of this event (erroneously) introducing the Japanese term in the context of an earthquake-generated, rather than a tidal, wave. Tsunami is also both the singular and plural form of the word in Japanese, but in English we generally append the "s" to make it plural.
(I was talking to a stranger in the Chicago airport yesterday and he commented that he hadn't heard the term "tsunami" until the 2004 tsunami devastated Indonesia. I reflected that even newspapers, radio and TV had limited impact until this 2004 event, which occurred coincident with the emergence of the modern internet. It would be interesting to survey the west coast, east coast, and midsection of the U.S. to see what tsunami awareness has been over the past century. My guess is that the west coast inhabitants would have been the most aware because of their exposure to earthquakes and tsunamis in the Pacific Rim, and that the east coast would have some awareness, perhaps correlated with a widely publicized (and controversial) prediction in 2001 that the collapse of the flank of Cumbre Vieja volcano in the Canary Islands would generate a 50 meter high tsunami around the Atlantic basin.)