Basically, bean curd is cottage cheese made by coagulating ground up and cooked soybeans (soy milk) rather than dairy milk. First appearing during the Chou Dynasty (1132-246 BCE), there are several theories for its origin, all of which are unadulterated speculation.
In this case, most, but not all, the toxins are drained away with the iquid. Two studies have linked high tofu consumption with low brain weight and cognitive decline. Others say this may be not from the beans, but due to aluminum from processing equipment - but that's scant comfort for someone who eats a lot of tofu. Many products, both Asian and Western, are made from tofu, and many of the important ones will be found on our Tofu / Bean Curd page.