'ataxic' originates from New Latin/modern medical coinage, specifically from New Latin 'ataxicus', ultimately from Greek 'ataxis', where the prefix 'a-' meant 'not' and 'taxis' meant 'order' or 'arrangement'.

'ataxic' changed from the New Latin medical adjective 'ataxicus', itself derived from Greek 'ataxis', and entered English medical usage in the late 19th century as 'ataxic'.

Initially it meant 'without order' (literally 'not ordered'), but over time it evolved into the specific clinical sense 'lacking coordinated muscle control' used in modern medical contexts.