The thing is, is that Doc's "double is" has been tracked by linguists...

[Ian Livingston]

Yeah, OED only tracks usage in print. Usage in the spoken language
generally (not always!) predates print usage, sometimes considerably.

On Mon, May 31, 2010 at 8:51 PM, Michael Bailey
<michael.lee.bailey at gmail.com> wrote:
> oh, gosh, my mom used to say, "The thing of it is, is..."
>
> she has a lot of quaint and curious phrases like that...
>



-- 
"liber enim librum aperit."