The term “They!” As an expression of surprise or silliness

So, I have been married 20 years to a fine woman from the Ozarks of Missouri. Her family regularly used the term they to make an expression.

It might be used like this:

The neighbors nearly burned their house down trying to defrost their turkey.

They!

Or even:

Storms are coming we make have to take shelter.

they!

I don’t know what to make of it, but I was watching a show about old times tonight and they used it.

Can anyone give me so etymology of this usage?

I grew up in western NC, and I vividly remember getting a test paper back in about 3rd grade which had a perfect score on it, and I exclaimed to myself, "They!" and some of my peers looked at me funny. So even in regions where the word is used like this, the usage is fading (that memory is from 35 years ago). We had three generations living in close proximity so we learned a lot of "old timey" words. "They" was used very often like this. Unfortunately, I can't speak to the etymology. My people are Scotch-Irish rooted in Appalachia, if that helps. I'll ask my dad, since he is quite a word nut!