Bletilla hyacinthina, hyacinth orchid. See Ludvik 2007, p. 310. Or possibly Rhizoma iridis. The root of the iris flower, specifically the Indian iris (Iris pallida). The root is said to resemble an arm, while the leaves resemble swords, and therefore there is a folktale of its having originated from Indra cutting off a yakṣa’s arm.

(Toh 557: dbang po’i lag)