'arsenotherapy' originates from Greek, specifically the words 'arsenikon' and 'therapeia', where 'arsenikon' meant 'arsenic' and 'therapeia' meant 'healing' or 'treatment'.

'arsenotherapy' was formed in Modern English as a compound of 'arsenic' + 'therapy'. The element name 'arsenic' itself came into English via Latin/French from Greek 'arsenikon', and 'therapy' comes from Greek 'therapeia' through Latin.

Initially, the term referred broadly to folk or early medical uses of arsenic for various ailments; over time it has come to denote both historical uses and specific, controlled medical applications (e.g., arsenic trioxide in leukemia treatment).