'arsenism' is formed in English from 'arsenic' + the suffix '-ism', influenced by French 'arsénisme', where 'arsenic' ultimately comes from Medieval Latin 'arsenicum' (from Greek 'arsenikon').

'arsenicon' in Greek gave Medieval Latin 'arsenicum', which passed into Old French as 'arsenic/arsénic' and later into English as 'arsenic'; the English noun 'arsenism' was then formed by adding '-ism' to denote the condition or practice related to arsenic.

Initially related simply to the substance 'arsenic' and its properties, the term evolved to name the condition or poisoning (i.e., 'poisoning by arsenic') now expressed by 'arsenism'.