"be active," 1570s (bustling "noisy or excited activity" is from early 15c.), frequentative of Middle English bresten "to rush, break," from Old English bersten (see burst (v.)), influenced by Old Norse buask "to make oneself ready" (see busk (v.)), or from busk (v.) via a frequentative form buskle. Related: Bustled; bustling; bustler.
"activity, stir, fuss, commotion," 1630s, from bustle (v.).
"padding in a skirt," 1788, of uncertain origin, perhaps from German Buschel "bunch, pad," or it might be a special use of bustle (n.1) with reference to "rustling motion."
BUSTLE. A pad stuffed with cotton, feathers, bran, &c., worn by ladies for the double purpose of giving a greater rotundity or prominence to the hips, and setting off the smallness of the waist. [Bartlett, "Dictionary of Americanisms," 1848]