repoussage

from The Century Dictionary.

• noun The beating out from behind of ornamental patterns upon a metal surface. See repoussé, n.
• noun In etching, the hammering out from behind of parts of an etched plate which have been brought by charcoal or scraper below half its thickness, making hollows which would show as spots in printing, in order to bring them up to the required level.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Art) Art or process of hammering out or pressing thin metal from the reverse side: (1) in producing repoussé work; (2) in leveling up any part of an etched plate that has been worked so as to cause a depression.