The word 钉子 is formed through a common morphological process in Chinese where a meaningful root character, 钉 (which depicts a metal nail and carries the core meaning of "to nail" or "nail"), is combined with the suffix 子. This suffix 子 often attaches to nouns, not to change the core meaning significantly, but to create a more concrete, stand-alone noun form, in this case solidifying the concept into the tangible object: "a nail". It's a straightforward compound where the root provides the semantic core and the suffix completes it as a standard, everyday noun.