According to PW. barhánā is an old instr. of a *barhána- from the 2 √ barh-, “kräftigen,” etc., and means adverbially: “dicht fest, derb, nachdrücklich, tüchtig”; emphatically “sehr, gar, recht eigentlich”. Grassmann, Wb. zum Rigveda, s.v. has: (1) “Kraft, Macht,” (2) “insbesondere Macht über jemand (gen.), (3) as an adverb: “mit Macht, kräftiglich.” In RV. 1, 166, 6, the word is used, according to him, to denote a weapon “wie etwa ein Schleuderstein”. So also for 8, 63, 7. Ludwig agrees on the whole with PW.