'arachnidism' originates from New Latin/Greek, specifically from the Greek word 'aráchnē' (ἄραχνη), where 'aráchnē' meant 'spider', combined with the noun-forming suffix '-ism' (via Latin/Greek) meaning 'state or condition'.

'arachnidism' changed from the scientific New Latin root 'Arachnida' and the English adjective 'arachnid' and eventually became the modern English noun 'arachnidism' by adding the suffix '-ism' to denote a condition related to arachnids.

Initially the roots referred to 'spider' or the taxonomic group Arachnida; over time the formed word came to mean specifically the medical condition caused by a spider or other arachnid's bite (envenomation).