Originally, there was a writeup on this node claiming that 'misspelt' was a mispelling. This is not the case. Spelt and misspelt are both slightly archaic, but they are English words.
MISSPELT', pp. Spelled wrong, or with wrong letters. -- Webster's 1828 Dictionary.
http://www.christiantech.com/cgi-bin/webster.cgi?search_for_texts_web1828=misspelt