I know nothing about Lakota or Dakota humour, but 'self-deprecating' humour is known as
sardonic humour, which comes from a greek word meaning "bitter or scornful laughter". It works by approaching adverse situations with pessimism, at the expense of the self. Its aim is to give relief from tension. The Spartans are known for this sort of humour too, e.g. "
Then we'll fight in the shade".
To create this humour is easy. Just give a character a difficult or dangerous situation (e.g. trying to cross a rickety bridge). Find a pessimistic outcome (I'll fall in the water), and then invent a dubious benefit (My wife says I should bathe more often anyway).
Often, the sardonic is funnier if you add irony - in which the speaker pretends to be mystified.
"Oh look... a woodcutter has dropped his kindling all across this river and made it look like a bridge."
"Well, your wife will be happy if we cross it - she always says we should bathe more."
And you can add a little sarcasm to the banter - especially among friends:
"You go first then - you're upwind of me."
"For good reason, my friend."
The key to good dialogue I think is to ensure that there is conflict, keep it indirect rather than direct, avoid triteness and make it colourful. Humour's hit and miss at the best of times, but at least colourful dialogue is entertaining.
"I always know when you're getting me into a fight, because the crows circle above me"
"Keep your shield upon your back then, and you'll be safe enough."
"I needn't outrun all the enemy, my brother - I only need to outrun you."
"Ah, but I have flat feet, so I may as well fight them."
"Well, if you're going to be fighting, then I'd better stay to coach you."
"Yell loudly then, so the foe down the back can hear."
