A dandan is a mythical sea creature that appears in volume 9 of The Book of One Thousand and One Nights, or Arabian Nights. It appears in the tale Abdullah the Fisherman and Abdullah the Merman, where the merman tells the fisherman that the dandan is the largest fish in the sea and is the enemy of the mermen.
References
Abdullah the Fisherman and Abdullah the Merman, from Richard Burton's 1885 translation
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