'antibiotic' originates from Greek, specifically the words 'anti-' and 'biotic' (from 'biotikos'), where 'anti-' meant 'against' and 'biotic' (from 'bios') meant 'life'.

'antibiotic' was formed in modern scientific English in the late 19th / early 20th century from New Latin/Modern Greek components (compare scientific New Latin 'antibioticus') and gained use in English via terms like 'antibiosis' and 'antibiotic' for substances acting against microorganisms.

Initially formed to mean 'acting against life' (in the sense of opposing living organisms such as microbes), it came to refer specifically to substances that kill or inhibit pathogenic microorganisms and, in modern usage, drugs used to treat bacterial infections.