What's the etymology of hammer, 金槌? Jisho.org gives "mallet" for the 槌 kanji. Is the "金" kanji indicating "metal", or "golden", presumably as in colour? The English edition of Wiktionary doesn't have etymology, and the Japanese edition of Wiktionary doesn't have an entry at all!
metal + mallet, hence (metallic) hammer (typically used to drive metallic nails). This 金 means metal, not golden color nor money.
槌 and ハンマー (in Japanese) refer to mallets and hammers in general, including ones with metal, wooden, plastic and rubber heads. To refer to what is typically referred to as hammer in English, you usually have to say 金槌.
We have a word 木槌【きづち】 (wooden mallet), too, which is basically the same as 木製のハンマー.