mullein n.

tall weed of the figwort family, used medicinally, early 14c., molein, probably from Anglo-French moleine (Modern French molène), perhaps literally "the soft-leaved plant," from French mol "soft," from Latin mollis "soft" (from PIE root *mel- (1) "soft"). This connection was felt in Middle English, and the word soft was used as an alternate name for the plant (early 14c.)

There is an Old English word molegn or moleȝn, which Cockayne identifies as mullein. The word is glossed in a manuscript with Latin calmum and Old English windelstreow, both of which suggest something straw-like, though this does not necessarily exclude mullein with its tall stalk and little stubble-like hairs. If the identification is correct, this would upset the French etymology.