Mercury probably refers to the poisonous liquid, while Mars may be a reference to Iron, since Mars represents the said Element in Alchemy .
Behind the scenes
- Mercurialis is a genus of plants in the family Euphorbiaceae, the spurges, known commonly as the mercuries. These are slender herbs (forbs), rhizomatious perennials and woody perennials. There is 1 Asian species and 8 to 10 European species (depending on classification) of which annual mercury and dog's mercury are highly poisonous. Rue is a herb belonging to the genus Ruta and was also known as Mars' herb by the Romans, because it was used as a purifiying agent for cleaning iron (the metal of Mars). Another reason is that its essential oil can be a very irritating agent and can easily cause burns and blisters on the skin if applied, which makes it as fierce as the God himself. It has a very bitter taste.
- In Harry Potter and the Chamber of Secrets (film), it was listed as an ingredient in a recipe for the Polyjuice Potion. Pottermore, however, presented a recipe that did not include it, being in-line only with the ingredients listed in the original Harry Potter and the Chamber of Secrets novel.