According to a theory, the difference between the two dialects is due to a rugged mountainous area along the coast that blocked traffics of people where Nagu is located..
奈具は海岸沿いの険しい山岳地帯であり、人の往来が出来なかったことが丹後弁と舞鶴弁の違いを生んだとの説がある。