Monier-Williams: A Sanskrit-English Dictionary (p. 54)
apāmārga, as, m. (√ mṛj), the plant Achyranthes aspera (employed very often in incantations, in medicine, in washing linen, and in sacrifices), AV.; VS. &c.

Tamil Lexicon, University of Madras (p. 660)
kaṭalāṭi: A plant growing in hedges and thickets

Tamil Lexicon, University of Madras (p. 2223)
nāyuruvi: A plant growing in hedges and thickets, l. sh., Achyranthes aspera

Tamil Lexicon, University of Madras (p. 449)
uruviyuppu: Medicinal salt made from Achyranthes aspera

Dymock, Warden, Hooper: Pharmacographia Indica (vol. III, pp. 135-136)
Achyranthes aspera, Amarantaceae
Fig. - Prickly Chaff-flower (Eng.)
Hab. - Throughout India and tropical Asia. The herb.
This plant has given a name to the sacrificial offering called Apamarga Homa, which consisted of a handful of the flour of the seeds offered at daybreak, but which is not now, as far as we know, practiced in India. According to the Black Yajurveda, Indra, having killed Vritra and other demons was overcome by Namuchi and made peace with him, promising never to kill him with any solid or liquid, neither by day or by night. But Indra collected some foam, which is neither solid nor liquid, and killed Namuchi in the morning between night and daybreak. From the head of the demon sprung the herb Apamarga, with the assistance of which Indra was able to kill all demons. Hence this plant has the reputation of being a powerful talisman, and is now popularly supposed to act as a safeguard against scorpions and snakes by paralysing them. (Compare with Scribonius Comp. 163, 164, where similar superstitions are recorded.) It is waved round the body whilst taking the ceremonial bath early in the morning on the Naraka Chaturdasi or first day of the Divāli (new year) festival.
The Sanskrit synonyms for the plant are Shikhari, Kini, or Kinihi, Khara-manjari "having a rough flower-stalk," Adhvashalya "roadside rice," Shaikharika, Pratyak-pushpi "having reverted flowers," and Mayuraka "crested." It is described in the Nighantas as purgative, pungent, digestive; a remedy for phlegm, wind, inflammation of the internal organs, piles, itch, abdominal enlargements, and enlarged cervical glands. The ashes are used by the Hindus in preparing caustic alkaline preparations. The diuretic properties of the plant are well known to the natives of India, and European physicians agree as to its value in dropsical affections; one ounce of the plant may be boiled in ten ounces of water for 15 minutes, and from 1 to 2 ounces of the decoction be given 3 times a day. (Pharm. of India, p. 184.)
Different parts of the plant are ingredients in many native prescriptions in combination with more active remedies.
In Western India the juice is applied to relieve toothache. The ashes with honey are given to relieve cough; the root in dosed of one tola is given at bedtime for night blindness, and rubbed into a paste with water it is used as an anjan (eye salve) in opacities of the cornea. The seeds are often used as a famine food in India, especially in Rajputana, where the plant is called Bharotha (grass).