The word "石头" is formed by combining two pictographic characters. The first character, 石, originally depicted a cliff (厂) with a stone (口) beneath it, directly representing the concept of "rock" or "stone". The second character, 头, is a simplified pictograph evolved from a drawing of a human head, representing the "head" or "top" of something. When combined, 头 here functions not literally but as a familiar, concrete suffix, attaching to the core idea of "stone" to form a single, common noun for a tangible, physical rock.