Wiktionary lists 錘, 槌, 鎚, and 椎 to all have the meaning of "hammer", but I'm not sure if that was the original meaning for any of those characters, and they all (or at least some) appear to have different origins and developments from each other. For instance, 說文解字 has the definitions for the following three characters:
None of these entries have hammer as a definition (although 椎 has the definition of "to strike"). 鎚 doesn't seem to be listed in 說文解字, so I'm assuming it was created later on.
How did all of these characters gain the meaning of "hammer", and how are these four characters related?