The word 饼干 (bǐnggān) is formed by directly combining two meaningful characters to create a new, composite idea. The first character, 饼 (bǐng), historically refers to a flat, round baked or cooked food item, like a pancake or flatbread. The second character, 干 (gān), means "dry". Together, they describe the essential nature of the food: a dry, baked flat cake, which perfectly captures the modern meaning of "biscuit" or "cookie". It is a logical, descriptive compound where the attributes of the object are literally named.