In my little headspace, it would be the grossest abuse to force a child to give you their dark-name. The most appalling, the most horrible abuse of trust. To do so makes you everything a Dwarf should not be. An un-Dwarf, basically. Exile would be the kindest thing to happen to you.

(sorta-kinda-maybe related: the Petty-Dwarves, a smaller variant of Dwarven people, were said to use their secret names openly (Silmarillion). The Petty-Dwarves were suggested to be normal Dwarves who were exiled from Dwarf society, possibly for some nameless crime. We don’t know. They all died out in the First Age. We do know that the Elves hunted the Petty-Dwarves for sport until they finally realised that they were sentient, though jeez seriously Elves ‘wisest beings’ yeah right wtf)

In Sansukh’s universe, it’s very common for a parent or parents to be the first one/s to hear their child’s Dark-Name. It’s about trust and openness and vulnerability. Their child feels safe and loved. And so, in a moment of sheer tender magic, the child tells their parents what is written into their bones, what words surge in their blood. It’s a moment that new parents long for and dream about: the highest and most sacred loving honour they can receive.

However, that’s not true of all Dwarves. There are (thankfully very rare) crappy Dwarven parents whose children cannot ever feel that perfect safety and trust needed. They would never want to give their parent such a huge part of them. These Dwarves would keep their Kherumel to themselves. 

I also think that some of the higher beings can see what is written into each Dwarf with such love in Mahal’s handwriting. So: Gandalf, Sauron, Saruman. Gandalf has better manners than to blurt it out, though. Saruman would probably use it to manipulate.

Sauron uses it to attack. It is obscene that he attacks each Dwarf (through the Ring) using that special, sacred name, the very heart of them. That is the most disgusting and profane and horrible thing he could possibly do.