'abnormally' originates from the Latin word 'abnormis', where 'ab-' meant 'away from' and 'norma' meant 'rule or pattern'.

'abnormis' transformed into the Medieval Latin word 'abnormalis', and eventually became the modern English word 'abnormal' with the adverbial form 'abnormally'.

Initially, it meant 'away from the rule or pattern', but over time it evolved into its current meaning of 'deviating from the usual or expected'.