'bacteriopsonic' originates from modern medical formation combining the combining form 'bacterio-' (from Greek 'bakterion', meaning 'small staff; rod', used for 'bacterium') and 'opsonic' (from Greek 'opson', meaning 'food; relish', via Neo-Latin/medical usage in 'opsonin'/'opsonize').

'bacteriopsonic' was coined in 20th-century medical English by blending 'bacterio-' + 'opsonic' (the latter derived from 'opsonin' in immunology); it does not descend from an Old English form but from Greek roots through Neo-Latin/medical usage.

The constituents originally meant 'rod-shaped organism' and 'food/sauce', but in medical usage they combined to denote 'promoting the coating of bacteria to enhance phagocytosis'; the term's modern specialized meaning in immunology has been stable.