'flagellum' originates from Latin, specifically the word 'flagellum', where 'flagellum' meant 'whip' (a diminutive of 'flagrum').

'flagellum' passed into Medieval Latin and New Latin (scientific Latin); the biological sense and the Latin plural 'flagella' were adopted into English primarily through scientific usage.

Initially, it meant 'whip', but over time it evolved into its current biological meaning of 'whip-like cellular appendage used for locomotion or sensation'.