It's been a misspelling for a while it seems https://books.google.com/ngrams/graph?content=impostor%2Cimposter&year_start=1800&year_end=2019&corpus=en-2019&smoo

It's been a misspelling for a while it seems https://books.google.com/ngrams/graph?content=impostor%2Cimposter&year_start=1800&year_end=2019&corpus=en-2019&smoothing=1&case_insensitive=true https://books.google.com/ngrams/graph?content=impostor%2Cimp...