'leukocyte' originates from New Latin/Modern scientific coinage, ultimately from Greek: 'leukos' (λευκός) meaning 'white' and 'kytos' (κύτος) meaning 'container, cell'.

'leukocyte' was formed in New Latin or 19th-century scientific terminology from Greek roots ('leukos' + 'kytos'), and this compound passed into English as 'leukocyte' with the same structure.

Initially it literally meant 'white cell' (a cell that appears pale or colorless); over time it has been used specifically for the various cells of the immune system (white blood cells).