'hair-splitting' originates from English, specifically from the phrase 'split hairs', where 'hair' meant 'a single strand of hair' and 'split' meant 'to divide.'

'hair-splitting' changed from the phrase 'split hairs' (recorded from the early 17th century) and eventually became the compound adjective and noun 'hair-splitting' in later usage to describe the act of making excessively fine distinctions.

Initially, it meant 'to divide a hair' (literal), but over time it evolved into its current meaning of 'making excessively fine or trivial distinctions.'