caiman n.

type of tropical American alligator, also cayman, 1570s, from Portuguese or Spanish caiman, from Carib acayouman "crocodile," or perhaps from a Congo African word applied to the reptiles in the new world by African slaves. "The name appears to be one of those like anaconda and bom, boma, which the Portuguese or Spaniards very early caught up in one part of the world, and naturalized in another." [OED]