Wordorigins.org

As most people know tsunami is a borrowing from Japanese. A tsunami is a series of large waves, caused by an earthquake or other underwater disturbance. The Japanese is a compound of tsu = “harbor” and nami = “waves.” The word first appears in English use in an article in the September 1896 National Geographic:

There were old traditions of such earthquake waves on this coast, one of two centuries ago doing some damage, and a tsunami of forty years ago and a lesser one of 1892 flooding the streets of Kamaishi and driving people to upper floors and the roofs of their houses.