Ragnaraku!!! = Besides being the apocalypse in Norse mythology (Ragnarok), literally in Japanese it means "descent to hell." The term for "hell" is more precisely naraka (Buddhist hell).
Hourai Hakke!!! = Roar of thunder from the 8 divine diagrams. Roar can be interpreted as "cannon." The wordplay is connected to the mythical Mount Horai, where 8 immortals from Japanese culture reside.
Dai itoku Raimei Hakke!!! = Thunder of the conquering death's 8 divine trigrams. It refers to another deity of wisdom, Yamantaka, from Buddhism who defeated Enma.