The word Arka has lots of meaning

As per Ancient Aryan Religion -

Arka plant is considered very special to Lord Ganesh & Shiva.

As per ayurveda -

Arks is a Sanskrit word referring to the "Milkweed" plant and is used throughout Ayurvedic, refers to the medicinal plant known as Calotropis gigantea, and is used in the treatment of poison and chronic disease.

As per Rasashastra -

Arka is the Sanskrit word translating to "copper", a pure metal commonly found in nature.

As per Modern Indian dictionary -

Arka is Spirit or essence, extract, essential oil, spirituous liquor.