Is it ensure, insure, or assure?
1721, "alloy of copper and tin," from French bronze, from Italian bronzo, from Medieval Latin bronzium. Perhaps cognate (via notion of color) with Venetian bronza "glowing coals," or German brunst "fire." Perhaps influenced by Latin Brundisium the Italian town of Brindisi (Pliny writes of aes Brundusinum). Perhaps ultimately from Persian birinj "copper."
In Middle English, the distinction between bronze (copper-tin alloy) and brass (copper-zinc alloy) was not clear, and both were called bras. A bronze medal was given to a third-place finisher since at least 1852. The archaeological Bronze Age (1865) falls between the Stone and Iron ages, and is a reference to the principal material for making weapons and ornaments.
1640s, literally, 1726 figuratively, from French bronzer (16c.) or else from bronze (n.). Related: Bronzed; bronzing. Meaning "to make to be bronze in color" is from 1792.
coating an object of wood, plaster, clay, or other substance to give it the colour and lustre of bronze. Dutch metal, an alloy of 80 percent copper and 20 percent zinc, is frequently used for bronzing. The metal is prepared as a thin foil and then powdered. This powder may be applied directly to objects that have been sized with a spirit lacquer or gold size, or the powder may be combined with spirit lacquer thinned with amyl acetate and the mixture painted on with a brush. Various shades of colour may be obtained chemically; the natural golden colour of Dutch metal can be heightened by applying spirit lacquer coloured with dragon's blood, a resin obtained from plants.