The clear, umami-packed stock called dashi is the foundation of washoku, traditional Japanese cuisine. While stocks made by simmering various umami-rich ingredients are important in many cuisines, it's hard to think of another where it plays as indispensable a role as it does in washoku.
One reason why dashi has become so ubiquitous is that methods for extracting it from easily stored ingredients were invented several hundred years ago. Long before the discovery of convenient glutamate packed concentrates, cubes and powders, Japanese cooks came up with ways of drying certain ingredients from which umami could be quickly and conveniently extracted. These dried ingredients are still used today, by home cooks and pros alike.
The earliest written record of the word "dashi" appears in the Kamakura Period (1185-1333), where it meant a kind of sauce used on white fish. There are even earlier mentions (dating back as far as the sixth century) of making stock by simmering fish or animal bones and vegetables, but these were not known as dashi. In the Muromachi Period (1392-1573), recipe books belonging to the Okusa-ryu (Okusa school) of culinary arts, which still exists today, are believed to contain the first record of using katsuobushi to make a broth, in a recipe for stewed swan. Katsuobushi is made by salting, drying and fermenting bonito fish, each step of the process designed to maximize the bonito's umami as well as allowing it to be preserved and stored in those pre-refrigeration days.