'misexpress' originates from Old English/Old Norse prefix 'mis-' (used in English) meaning 'wrong(ly)' and from the verb 'express', which ultimately comes from Latin 'exprimere' where 'ex-' meant 'out' and 'primere' (from Latin 'premere') meant 'to press'.

'express' changed from Latin 'exprimere' to Old French 'esprimer'/'exprimer' and then to Middle English 'expressen', eventually becoming the modern English 'express'. The prefix 'mis-' has Germanic/Old English roots ('mis-') meaning 'wrong' or 'badly', and was attached to verbs to indicate incorrect or negative action, producing 'misexpress' (to express wrongly).

Initially, 'express' literally related to 'pressing out' in Latin, but its meaning shifted to 'conveying thoughts or feelings'; combined with 'mis-' the compound has meant 'to express wrongly' since formation and retains that meaning today.