I had not thought about it before, but tidal waves are not tidal.
Tidal forces, which cause normal ocean waves, are from the sun’s and moon’s gravity. This explains why the cycle of high and low tides is regular—because the orbits and rotations of the sun/earth/moon system are regular.
So, tidal wave should just mean a normal wave. But most people understand tidal wave to mean a gigantic wave, a freak of nature.
The problem is, such waves have nothing to do with tides. They are caused by sudden displacements of ocean water due to earthquakes, volcanoes, or other major disruptions. Thus, scientists prefer the term tsunami to describe one or more massive waves caused by an irregular event.
I had always assumed that tidal wave and tsunami were either equivalent or subtle variants. Now I know, tidal waves are just big misnomers. Thanks to Jacqueline for enlightening me.