'septicaemic' originates from New Latin/modern medical formation, ultimately from Greek 'sēpsis', where 'sēptikos' meant 'putrefaction' or 'causing decay'.

'septicaemic' developed from the medical noun 'septicaemia' (from Late Latin/Modern Latin 'septicaemia' and French 'septicaémie') and was adapted into English as the adjective 'septicaemic'.

Initially associated with the idea of 'blood putrefaction' (blood poisoning), the term evolved to mean 'relating to or caused by septicaemia (sepsis)' in modern medical usage.