'atoxyl' originates from a modern (19th-century) coinage based on Greek via scientific/trade-name formation; specifically from Greek 'toxikon' (from 'toxon') where the prefix 'a-' meant 'not' and 'toxon' meant 'poison' (the name was intended to suggest 'non‑toxic').

'atoxyl' was coined in the late 19th century as a trade/scientific name for an arsenical compound; the term appeared in French and German medical literature and was adopted into English as the name of that drug.

Initially the formation suggested 'non‑toxic' (a‑ + tox‑), but over time the word came to denote a specific arsenical medicine that proved to be toxic, so the implied 'non‑toxic' sense is misleading/ironic.