🎂 So at least some dwarves in your world speak by tapping little hammers on the rock around them. Do they have a way of speaking above ground? And how did specialized speaking hammers come to be thing? What did they do before they invented the hammers or if they don't have one with them?
The Hulfraust nation developed their language of taps and strikes as a more effective way to communicate with each other in loud forges and smithies. They use their hammer-like malatol tools to strike stone or metal when either is handy. If they are above ground they will typically use their malatol on a pauldron, belt buckle, or some other piece of metal that they are wearing.
If they don’t have a malatol anywhere nearby (which is rare since they tend to carry them everywhere) they will use their tongues to make click and clack sounds that mimic the sounds of the malatol. This is the method that Hulfraust children are taught to use for communicating, and receiving their first malatol is considered an important rite of passage into adulthood.