zaratan
In Arabic folklore, an extremely large (sea) turtle, the shell of which resembles an island.
[…]turtle known as zaratans. Living for millennia, these slow-moving gentle giants dine exclusively on sea […] a zaratan's shell grows ever more complex as it ages.
Where it comes from
Ultimately from Arabic سَرَطَان (saraṭān, “crab”), possibly via Spanish zaratán.
Adapted from the Wiktionary entry zaratan (CC BY-SA 4.0).