the.com/tidal wave

means A huge, destructive surge of ocean water sweeping onto land — though strictly speaking, most of these are caused by earthquakes, not tides, which is why scientists prefer 'tsunami.'

from From 'tidal' (relating to tides) + 'wave,' a straightforward 19th-century English compound coined when people assumed these giant waves were an extreme version of ordinary tidal action. Science later caught up: most are triggered by undersea earthquakes, volcanic eruptions, or landslides, not the gravitational pull of the moon and sun. The Japanese word 'tsunami' (harbor wave) became the technical term precisely to escape this misleading tidal association — but 'tidal wave' had already lodged itself in everyday speech and refused to leave.