Why is the ninth month called September?
"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]
item of feminine apparel for pushing out the skirt in back just below the waist; although used at various times since the 14th century, it was first known under this name in the 19th century. The specific fashion for the bustle, or tournure, came between 1865 and 1876 and again in the 1880s. It followed the decline of the crinoline (q.v.) and began as a bunching up of material behind the waist but became a wire cage attached to the petticoat, sticking out backward like a shelf, over which the dress material was draped.