'misword' is formed in modern English from the prefix 'mis-' (from Old English 'mis-', meaning 'wrongly' or 'badly') + the noun 'word' (Old English 'word', meaning 'word').

'mis-' is an Old English prefix used to indicate error or wrongness; combined with 'word' the compound 'misword' follows regular English word-formation, with the past/past-participle 'misworded' formed by adding the regular suffix '-ed'.

Originally the elements meant 'wrong' + 'word' (i.e., to use words wrongly); over time the compound retained this basic sense and is used to describe phrasing that is inaccurate, inappropriate, or misleading.