'bacteriologist' originates from Modern English, built from 'bacteriology' + the agent suffix '-ist'. 'Bacteriology' comes from New Latin 'bacterium' + Greek-derived '-logy' (from Greek 'logia' meaning 'study' or 'science'), and 'bacterium' ultimately from Greek 'bakterion' meaning 'small staff' or 'rod'.

'bacterium' entered scientific Latin in the 19th century from Greek 'bakterion.' From this came 'bacteriology' (the study of bacteria) in the mid-1800s, and then 'bacteriologist' (one who studies or works with bacteria) appeared in English in the late 19th century.

Initially it referred specifically to scientists studying bacteria; over time the meaning has remained largely the same, broadly covering researchers who investigate bacterial biology, ecology, and medical implications.