Cimorene

The etymologists were suggesting that a confusion of accent was the origin of the divergence/the "thing" form, not that it's a separate occasion of mispronunciation every time it's spoken, so Simon's accent wouldn't have to confuse the two sounds, he would just have to speak a dialect that uses the "thing" form (but in fact the issue is whether the accent would require separate enunciation of two k sounds: think(.)coming. I can't think of any accent offhand that would pronounce it that way outside of deliberate emphasis). The origin would have to have been decades ago at least for the forms to be so close to neck-and-neck in usage as they are today (and for 80% of users of each form to be unaware of the existence of the other!).

I can't really see how they could have separate meanings. How would you parse the significance of the phrase with "thing"? What would it mean that was different from the version with "think"? The beginning of the expression refers to assumptions and doesn't imply anything about objects of any kind.