词源不确定，可能来自 scad 的复数形式，引申词义大量，许多。
In July, 1834, as Mr. Yarrell informs us, most extraordinary shoals passed up the channel along the coast of Glamorganshire; their passage occupied a week, and they were evidently in pursuit of the fry of the herring. The water appeared one dark mass of fish, and they were caught by cart-loads, and might even be baled out of the water by the hands alone. ["British Fish and Fisheries," 1849]
来自《权威词典》
来自《简明英汉词典》
牛津词典
《简明英汉词典》
《牛津高阶英汉双解词典》