When the Spaniards first saw this reptile in the New World, they called it el lagarto (the lizard). Sir Walter Raleigh called these creatures lagartos, and Ben Jonson alligartas.
“To the present day the Europeans in Ceylon apply the term alligator to what are in reality crocodiles.” —J. E. Tennent: Ceylon (vol. I. part 2, chap. iii. p. 186).
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894