The story
Probably from ada(mantyl) + p(henyl) + (naphth)alene.
Etymology from Wiktionary, CC BY-SA 4.0.
adapalene
Today it means: A retinoid C₂₈H₂₈O₃ applied topically to the skin in the treatment of acne vulgaris. It is marketed under the trademark Differin and when used in combination with benzoyl peroxide, under the trademark Epiduo. Full definition →