Do you know what howdy means? You probably answered that howdy means hi, well you might be wrong.
Let's break it down:
           How d y
Now let's add a few letters:
           How do you?
I think howdy is just a shortened version of "how are you?" and in olden times they used to say "how do you?" instead of "how are you?"
--------------------------------------------------
So what do you think? Do you agree?