'patchy' originates from English, specifically from the noun 'patch' combined with the adjectival suffix '-y', where 'patch' meant 'a piece or area of something' and '-y' formed an adjective meaning 'characterized by'.

'patch' changed from Middle English forms such as 'pach(e)' and Old French influences into the Modern English noun 'patch'; the adjective 'patchy' was later formed from this noun with the suffix '-y'.

Initially it meant 'consisting of or made of patches', but over time it evolved into its current sense of 'uneven, incomplete, or occurring in patches'.