'mismade' is formed in English from the prefix 'mis-' (from Old English 'mis', meaning 'badly' or 'wrongly') combined with 'made', the past participle of 'make' (from Old English 'macian').

The prefix 'mis-' goes back to Proto-Germanic *mis- meaning 'wrong' and combined with Old English 'macian' (to make) produced Middle English compounds (e.g. 'mis-' + past forms of 'make'). Over time these combinations yielded adjectival or participial forms such as 'mismade' in modern English.

Initially it simply indicated something 'made wrongly' (the literal combination of 'mis-' + 'made'); over time it has retained that basic sense and is used adjectivally to describe poorly made objects or to indicate a mistaken act of making.