Mokume Gane translates closely to "wood grain metal" or "wood eye metal". It is a Japanese metalworking process that creates a mixed-metal laminate with distinct layered patterns. This is a result of the principle of diffusion. Diffusion is the bonding of layers of metal, without the use of solder or flux, using a two or more different colored metals or alloys.
Mokume-Gane was invented by Denbei Shoami, in the time of the Samurais (1651-1728). He was a master craftsman who was supported by Satake, the feudal lord in the Akita area.
Shoami named his technique "Guri Bori" because the patterns on his first nonferrous tsuba (sword hilt) was like "Guri",
a Chinese lacquer technique in which patterns are achieved by carving into thick layers of different colored lacquer.
Because he understood how steel could be formed into patterned laminates, he translated that knowledge into nonferrous metals and alloys. He later named this pattern Mokume-Gane. His oldest work in Mokume-Gane was used in the creation of sword hilts, using gold, silver, Shakudo, and copper.
To read more about how Mokume Gane is made, and it's history, you can go the the Society of American Silversmiths website.