'acategorical' originates from the prefix 'a-' meaning 'not' or 'without' and the word 'categorical', which comes from the Greek word 'katēgoria', meaning 'category'.

'categorical' changed from the Greek word 'katēgoria' to the Latin 'categoricus', and eventually became the modern English word 'categorical'. The prefix 'a-' was added to form 'acategorical'.

Initially, 'categorical' meant 'pertaining to a category', but with the prefix 'a-', it evolved to mean 'not fitting into any category'.