What does arnica mean?
The definition of arnica
Ar”ni*ca, n.
Etym: [Prob. a corruption of ptarmica.] (Bot.)

A genus of plants; also, the most important species (Arnica montana), native of the mountains of Europe, used in medicine as a narcotic and stimulant.

Note: The tincture of arnica is applied externally as a remedy for bruises, sprains, etc.