1 Alvissa: Ardaxar told us where the Ruby of Dwarven Might is.
1 Dwalin: In his citadel. Boot 'tis booried oonder toons o' rooble noo! {translation: In his citadel. But it's buried under tons of rubble now!}
2 Alvissa: Not quite. He said it would be in his citadel half an hour after we asked. But he lied.
3 Dwalin: Soo 'tis nae booried oonder toons o' rooble noo? {translation: So it's not buried under tons of rubble now?}
3 Alvissa: Right!
4 Dwalin: Ah. Well thut narroos it doon. {translation: Ah. Well that narrows it down.}
4 Lambert: Hey, make him say that again!

Interestingly, a Google search on the topic of "Scottish dwarves" brings up lots and lots of pages of people asking questions like "Why are dwarves depicted with Scottish accents?" and "Since when did dwarves become Scottish?" and "What's with the stupid dwarves==Scottish thing??" and nothing actually explaining where this trend has come from.

It seems nobody out there likes it, everyone thinks it's ridiculous, it makes no sense whatsoever... and yet everyone does it. Me included!

What the heck is going on here?

(Well, speaking for myself, I do it because I'm copying all those other sources and I happen to think it's hilarious. If I was writing a serious novel or something as opposed to a humorous webcomic, I'd almost certainly do it differently.)

EDIT: A reader points out this conversation and supports the notion that the accent comes from the collision of two stereotypes: Scottish engineers, and dwarves being represented as engineer-types, who mine and build things and generally get stuff done.