The word 骨头 is formed by combining two characters: 骨 (gǔ), which pictographically represents the structure of a bone with its nodules and shaft, and 头 (tou), a very common suffix that, when attached to a noun stem, gives it a concrete, tangible, or everyday feel. The combination does not create a new meaning from separate parts ("bone" + "head"), but rather 头 functions to nominalize and solidify 骨 into the common, spoken word for "bone" as a physical object, making the term feel complete and colloquial.