What's the deal with "thank you kindly"?

Other questions on this site have established that kindly can be used as a sort of please. This usage was in my mind when someone said "Thank you kindly" to me, but "thank you please" doesn't make sense. However, characterizing one's own thanks as kind also sounds unlikely. The actual usage appears to be the sixth definition by Dictionary.com:

kindly
6. cordially or heartily: We thank you kindly.

However, I still have questions. Is this usage of kindly only used with thank you? How did this usage occur?

Solution 1:

Where I live (SE USA), kindly still is very much in use, but mainly as a way to exaggerate politeness, sometimes tongue in cheek. The word does not literally mean the same thing in thank you kindly as it does in would you kindly?, but in both cases it carries the connotation of being so polite that it sounds a bit silly, which makes it polite again. I realize that makes no sense whatsoever but I suppose it's a Southern thing and ask that you kindly make allowances.

Solution 2:

The usage has been around a long time, but it's been tailing off over the past century. Many might consider it dated or even archaic today. As OP has noted, the word kindly in "Thank you kindly" has the sense of "with goodwill and enthusiasm; very much", which has all but disappeared today outside of a few stock phrases.

For example, He kindly embraced him, is an old citation which IMHO has that meaning. And Wilkie Collins in The Woman in White (1861) has "[his lordship] was most kindly anxious to know what had become of her", which I read more as "very much" rather than "generously". In modern parlance the only other surviving usage with this meaning that I can think of is in constructions like "I didn't take kindly to being ignored", where it's in the negative.

But you could (erroneously, IMHO) parse it as "I thank you, kindly sir", so that "kindly" modifies the person being thanked (for having been kind to you). I wouldn't promote this idea too strongly, but as a subtext it might help the usage stick around. Certainly some of the comments against the question suggest this interpretation does at least occur to people, though I don't think it's central to the history of the usage.

Solution 3:

"Thank you kindly" is a very warm, humble, and appreciative form of thanks. It may be over-the-top, but if so it's in the same manner as "thanks a million!" As @JeffSahol noted, it is quite common in the southern USA, and I have a particular association with it being said by performers thanking their applauding audiences.