Other Crap

The 10 Greatest Impostors in History

By the way, Google returns about the same number of hits for "impostor" and "imposter," between a million and a half and two million in both cases.

According to OED, they also have equal historical claims. Edward Topsell’s History of Four-footed Beasts used "imposter" in 1607, while Shakespeare used "impostors" in MacBeth, circa 1605.

Neither was incorrect. There was no official spelling at that time. Although there were dictionaries in the 16th and 17th centuries, Dr. Johnson's was the first one considered authoritative, and that was published a century and a half later.