'banderillero' originates from Spanish, specifically from 'banderilla' + the agentive suffix '-ero', where 'banderilla' meant 'little flag' or 'small banner' (a diminutive of 'bandera').

'banderilla' developed in Spanish as a diminutive of 'bandera' ('flag' or 'banner'); the agent noun 'banderillero' (one who uses banderillas) formed from that Spanish base and was later borrowed into English contexts describing bullfighting.

Initially, the root referred to a 'little flag' or diminutive of 'flag'; over time 'banderilla' came to denote the decorated dart used in bullfighting and 'banderillero' came to mean the bullfighter who places those darts.