The Japanese call them "tsunamis", meaning "harbour waves", because they reach a sizable height only in harbours.
日本人称其为“海啸”,意思是“港湾浪”,因为它们只有在港口才能达到相当高的高度。
As the Roman Empire grew, the Romans needed to take control of the seas and for this they needed to build harbours capable of holding a fleet of ships.