'bacteriologist' 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 'bacterium', and eventually became the modern English word 'bacteriologist' through the addition of '-logist'.

Initially, it meant 'one who studies bacteria', and this meaning has largely remained the same in modern usage.