noun
ōnamazu; giant catfish thought to cause earthquakes
In Japanese mythology, a giant catfish believed to live underground and cause earthquakes by thrashing about. Often depicted in Edo-period prints.
江戸時代には、地震はオオナマズが暴れるからだと考えられていた。
In the Edo period, earthquakes were thought to be caused by the thrashing of a giant catfish.
この浮世絵には、鹿島神宮の神様がオオナマズを押さえつけている様子が描かれている。
This ukiyo-e print depicts the deity of Kashima Shrine pinning down the giant catfish.
ナマズ is the ordinary catfish; オオナマズ specifically refers to the mythological giant catfish associated with earthquakes.
From 大 (ō, 'big') + 鯰 (namazu, 'catfish'). The mythological association with earthquakes dates back to the Edo period.