In virtually every cuisine on the planet, there are attempts to dress food up and make it look like something it isn't. Whether it's a classical Chinese cook carving vegetables to make them look like a phoenix, or a French chef twisting his bread dough to resemble a lobster, food often appears in costume. There are many examples of this phenomenon in Japanese cooking as well, and sometimes the intention goes beyond just trying to delight the eating public.
There is at least a 1,000-year history of grilled fish pastes and steamed fish mousse in Japan. More recently (but still at least 100 years or more ago), cooks started molding and coloring fish paste to look and taste like crab meat. Whether it was an enterprising sushi chef who wanted to please his customers with a cheap alternative to crab, or a nobleman's cook who was trying to delight a bored patron, surimi was born.
In Japan, surimi is called what it actually is (the word means ground meat). In the United States, where surimi is the star of the now ubiquitous California Roll, regulations require food manufacturers to label it as imitation crab meat. Most of the surimi consumed today is made of pollack or Pacific whiting, caught and quickly frozen in Alaska before being shipped to Japan or China, where it is seasoned, colored and cooked.