Today, "cackle" is often used to mean a sharp laugh. But in its earliest uses, "cackle" referred to the sharp broken noise or cry that a hen makes especially after laying an egg. If you've ever heard a chicken cackle, you probably understand how people came up with the word. The hen's noise sounds something like "cackle." People have always made up words like "mewl" and "cackle," inspired by how things sound. The word for this is "onomatopoeia." Some other words that are examples of onomatopoeia are "clash," "honk," "thump," and "zoom."