'bacterium' originates from the Greek word 'baktērion,' which is a diminutive of 'baktēria,' meaning 'staff' or 'cane,' due to the rod-like shape of some bacteria.

'baktērion' transformed into the Latin word 'bacterium,' and eventually became the modern English word 'bacterium.'

Initially, it referred to a 'small rod,' but over time it evolved into its current meaning of 'a single-celled microorganism.'