How people spoke in the old west
The English language is under constant change and film-makers have to balance what they know to be accurate with what makes for the best drama. What I found most notable, and noteworthy, in the Coen brothers version of True Grit, is the lack of contractions. That is, a character would say, "I am going to the store", instead of "I'm going to the store". It makes the dialogue sound a bit stilted to our modern ears, but I liked it. And no, there are no recordings of voices from the era, but we know how people spoke because of books.
One of the most popular pastimes in "the old west" was playing cards, and it made it's way into ordinary language. When Sheriff Rooster Cogburn shouts, "Fill your hand!" he is referring to the game of poker. In poker, you are able to discard cards that you don't want, and fill your hand with, hopefully, cards that you do want.
You still hear these types of expressions used, especially where my family is from, in Minnesota, in the expression "A good deal" (as in being dealt a good hand of cards), and "you bet!"
Posted by Brad Hall