Fermented fish sauce
Cuisines around the world have used various forms of fermented fish sauce as a condiment or ingredient, since ancient times. The details of preparation can be unpalatable to some, but they basically involve fermenting seafood in salt, and obtaining distinctively flavored extracts. While they are primarily flavorings, they also can have a high protein, as well as sodium, concentration. Fermented fish products historically developed as a result of the limitations of transportation and an absence of refrigeration. Because of poor roads and slow transportation speeds, the provision of fresh fish to potential inland customers as well as storage was inhibited, and this encouraged fermentation as a preservation technique.
Fish sauces simply are not as obvious in Europe as in Asia. 
While many think of this as an Asian flavoring, garum was a basic element of cooking in the Roman Empire, and the very British Worcestershire sauce has fermented anchovies as one of its core components, although tamarind is another part of its distinct taste.
The smell of garum during the process of fermentation was said to be so foul that Roman citizens were actually outlawed from making it in their own homes. Roman production occurred on an industrial scale with areas of vats set aside near fishing ports throughout their empire, for the salting and fermentation process, and the sauce transported to markets in sealed barrels. Top quality garum was typically made from the viscera and blood of mackerel. Second grade was muria, made from tuna fish, and the third, 'poor mans' liquamen was made from any other fish available. According to the Roman historian, Pliny, the garum made in Barcino (Barcelona) was considered the best money could buy. He even gave his name to it, Pliny Garum.
Anchovy paste, as well as anchovies, are common.
Other fish sauces, such as botarque and ostardies, were produced in Italy and Greece in the 18th and 19th centuries. Another sauce reported to be produced in ancient Greece was aimeteon, which was made from Tunny viscera and blood.
Worcestershire is actually a British modification of an Indian idea. Lea & Perrins, the best known manufacturer, keeps the exact recipe secret. Competitive sauces, such as HP, have similarities but their own distinct flavors.
Southeast Asian kitchens and tables, however, are bare without fish sauce, and fish sauces also are common in East Asia.
The basic Vietnamese cuisine term is nuoc mam (nước mắm), but that is somewhat like saying "wine" in France; there are many distinctive preparations and grades. Some premium forms that are labeled to their place of origin, such as Phu Quoc and Phan Thiet. If the place name contains hon, Vietnamese for "island", it tends to mean that the manufacturing is local and higher quality.  Nuoc mam nhi comes from the first pressing of the fish and is considered a higher-quality condiment, with lower grades perfectly adequate for cooking.
Some American veterans of the Vietnam War brought back unpleasant memories, perhaps embellished with memories and storytelling, of reeking nuoc mam. Other Americans, however, routinely use it and find it has only a slight smell, but potent flavoring properties different from fermented soy.
It had a sufficiently distinctive smell, however, that some elite soldiers avoided using it, just as urban South Vietnamese soldiers avoided Brylcreem and other highly scented hair preparations. Under jungle conditions, a scout could sometimes smell the enemy. 
In Thai cuisine, the term is nam pla, also called "fish soy." Premium brands include "Squid", "Golden Boy", and "Tiparos".
The Burmese version is ngan-pya-ye
A common Filipino name is batis. Fermented shrimp is also common.
Begun in Thailand and finished and bottled in Hong Kong, Three Crabs is primarily exported to the United States, and contains sweetenings a more typical Asian sauce would not.
Not strictly fish, these are related preparations from Asia: sauces, pastes, or dried forms of fermented shrimp or other ingredients.
Oyster sauce is a Chinese ingredient made from oysters cooked with other ingredients, cooled, stained, and bottled.
Kimchi recipes often include oysters or shrimp: fresh, fermented, or dried.
Many Tahitians enjoy fafaru, a "piquant condiment" employed as a dipping sauce. Resembling clear water, it is made by placing crushed freshwater shrimp heads into a coconut gourd filled with fresh seawater, along with, perhaps, pieces of tuna fish; the coconut is then hung in the sunlight for a few days, after which the fafaru is strained and bottled. The taste is said to be surprisingly mild and agreeable, but the odor is horrendous. At many large Tahitian feasts a separate table, situated well-downwind from the other guests, is provided for those who wish dip their food into the fafaru.
- Fish Sauce / Nam Pla / Nuoc Mam: Fish Sauce Characteristics, Clay's Kitchen
- How to Buy Fish Sauce: A guide, Viet World Kitchen, 30 November 2008
- Skaidrite Mallah (1967), Cultural and Biological Effluents of Southeast Asia, Center for Research in Social Systems, American University, a U.S. Army contract research center
- How Douglas L. Oliver (1913-2009), a noted professor of Polynesian anthropology at Harvard once described it in the course of an undergraduate class