Jon Lighter on ADS-L yesterday, offering “An early “is is”:
1964 Jere Peacock To Drill and Die (N.Y.: Bantam) 257:
[(1)] “The thing of it is,” Waldron said … “is that this order was set up for you personally.”
The earliest example of Isis on record up to this point is from Dwight Bolinger in 1971 (details in a 2007 handout of mine, “Extris, extris”); 1964 would be an antedating, but not a remarkable one. Still, I’m dubious that (1) is a report of Waldron saying:
(2) The thing of it is is that this order was set up for you personally.
More likely it’s a report of:
(3) The thing of it is, …is that this order was set up for you personally.