brass
鍮 centers on brass, a specific copper-zinc alloy. The meaning is narrow and concrete, referring to the metal itself.
鍮 combines 金 (metal) with 俞, which likely contributes the sound. The character was created specifically to name the alloy brass.
The left side is metal 金, and the right side 俞 looks like a container. Picture a brass vessel made of this golden metal: 鍮 is brass.
For チュウ, imagine chewing on a piece of brass (don't actually do it!): chew -> チュウ, and the metal is brass.
—