'hemolysin' originates from Greek elements: 'haima' (blood) and 'lysis' (loosening, breaking), with the protein suffix '-in' from modern chemical/protein naming.

'hemolysin' was formed in scientific Neo-Latin/modern English by combining the Greek-derived combining form 'haemo-' (from Greek 'haima') + 'lysis', plus the protein suffix '-in', and has been used in biomedical contexts since the 19th–20th centuries.

Initially formation emphasized the process 'blood breaking' (literally 'blood dissolution'); it evolved into the current technical term for substances (usually proteins) that cause hemolysis.