The
animal known as the alligator was known in English as the lagarto or aligarto (and other variations) until
Shakespeare's time. These names can be traced to the
Spanish phrase "el lagarto" ("the
lizard"), which in turn derives from the
Latin word for "lizard," "lacerta". The English spelling, however, does not approximate alligator until the First Folio of Shakespeare’s works in 1623; the Folio uses the spelling "allegater".
In the last act of Romeo and Juliet, the servant Balthasar reports to Romeo about Juliet’s supposed death. The despairing young lover plans his own suicide by securing poison from a nearby apothecary who keeps "in his needy shop a tortoise hung, / An alligator stuff’d, and other skins"(V.i.42-43).
Shakespeare makes no further reference to this animal, but that use of the "r" to end its name became accepted, and by 1699 alligator was established in its current spelling.