About twenty-five years ago, at a Highland festival in Colorado, I was shown a book about the Scots language. I've no idea where it came from or the scope of its authority, if any. The example that I recall had to do with the word, "raither," with an "i" in the middle of it.

In English, it's "I would rather do this than that."

In Scots, the parallel given was "I had raither do this as that."

I can't and won't claim that I'm right about this. I don't even know if anyone in Scotland ever says this in this way. I merely mention it to show that it's been treated as a worthy topic by academics for a while now. The point that I took from the person who showed the book to me was that the Scots language has its own grammatical rules, and that these do not always happen to be the same as the rules of the English language.

Anecdotal bit of information: there are places on the prairies of the United States in which "I had rather do this than that" is the most common way of expressing the thought. I'm inclined to guess that they're partially following their ancestors' usage rather than having made up the construction out of whole cloth.