'bacterially' originates from English, specifically the adjective 'bacterial' (with the suffix '-ly' meaning 'in the manner of'), ultimately from New Latin 'bacterium', where the Greek root 'bakterion' meant 'small staff' or 'rod'.

'bacterially' developed from the adjective 'bacterial' (modern English), which came from New Latin 'bacterium' (used in scientific Latin to name bacteria); 'bacterium' itself was coined from Greek 'bakterion' and entered scientific usage in the 19th century, eventually yielding English derivatives such as 'bacterial' and then the adverb 'bacterially'.

Initially the root referred to a 'small staff' (the shape of certain microbes); over time it became the scientific term 'bacterium' for the organism and then adjectives/adverbs meaning 'relating to or caused by bacteria', which is the current meaning of 'bacterially'.