google ngrams can be quite entertaining when comparing spellings of words: https://books.google.com/ngrams/graph?content=mispell%2Cmisspell&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cmispell%3B%2Cc0%3B.t1%3B%2Cmisspell%3B%2Cc0