'bacteriological' originates from 'bacteriology', which is derived from the Greek word 'bakterion', meaning 'small staff or rod', and the suffix '-logy', meaning 'study of'.

'bakterion' transformed into the New Latin word 'bacterium', and eventually became the modern English word 'bacteriology', leading to 'bacteriological'.

Initially, it meant 'study of bacteria', but over time it evolved into its current meaning of 'relating to bacteriology or bacteria'.