1 Kyros: Actually, we came through the mountains via the Secret Dwarven Kingdom of Dwergenberg.
2 Dwalin: Dinnae be tellin' him aboot it! It's a sikkrit, ye gritt dongle! {translation: Don't tell him about it! It's a secret, you fool!}
3 Villager: Secret Dwarven Kingdom?! In the mountains?! Wow!
4 Kyros: Well, it's abandoned and overrun with orcs.
4 Dwalin: Will ye shoot oop alriddy! {translation: Will you shut up already!}

A dongle is actually a real thing.

I'm not entirely sure why a dwarf in a fantasy world would call someone one of those, but it works.

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2019-01-12 Rerun commentary: It probably means something rather rude in dwarvish.

It certainly makes Dwalin look a lot angrier in panel 2 than he normally looks.