'Mackintosh' originates from Scottish Gaelic, specifically the phrase 'Mac an Tòisich', where 'mac' meant 'son' and 'tòisich' meant 'leader' or 'chief'.

'Mac an Tòisich' was Anglicized to the surname 'Mackintosh'. In the 19th century, the name of Charles Macintosh (often spelled without a k) became associated with the rubberized waterproof coat he developed; the surname form (often spelled 'mackintosh' or 'Mackintosh') then came to denote that kind of raincoat. Later, the name was also used commercially (e.g., confectionery by Mackintosh).

Initially it meant 'son of the leader' as a family name, but over time the word also came to mean the rubberized waterproof coat named after an inventor and, separately, a commercial brand.