'miscounted' originates from English, combining the prefix 'mis-' (from Old English 'mis-' meaning 'wrongly') with 'count' (from Old French 'conter', ultimately from Latin 'computare' meaning 'to calculate' or 'to count').

'miscount' was formed in Middle English by attaching the negative/qualifying prefix 'mis-' to 'count'; the past/past-participle form 'miscounted' developed by adding the regular English verbal suffix '-ed'.

Initially it referred simply to making a wrong count ('to count wrongly'), and over time it has retained that basic sense with little change, now also used adjectivally to describe totals or items that have been counted incorrectly.