'arnica' originates from New Latin, specifically the botanical name 'Arnica', which was borrowed from French 'arnica'. The French term is believed to derive ultimately from Greek 'arnikē' (ἀρνίκη), possibly related to 'arnion' (ἀρνίον) meaning 'little lamb', a reference to the soft, woolly hairs on the plant's leaves.

'arnica' passed from Greek origins into French as 'arnica' (early modern period), was adopted into New Latin as the genus name 'Arnica' in botanical usage, and eventually entered English as 'arnica' with the same spelling and botanical/medicinal sense.

Initially it referred to the plant itself (members of the genus Arnica); over time the word also came to denote medicinal preparations made from the plant (topical ointments/creams) in common usage.