"large wave which rolls over and inundates the land," 1896, in reference to the one that struck Japan that year on June 15, from Japanese tsunami, from tsu "harbor" + nami "waves."

"of, pertaining to, or cause by the tides or a tide," 1807, a hybrid formation from tide (n.) + Latin-derived suffix -al (1). Also generally, "characterized by periodical rise and fall or ebb and flow."

A tidal wave (1819) properly is high water caused by movements of the tides; its use for "great ocean inundation caused by an earthquake, etc." is recorded by 1868. This now tends to be called a tsunami. Figuratively, "widespread manifestation of strong feeling," by 1870.