I am also from the American South, and in our dialect I think that gumption also implies initiative and staying power. I have never heard any Southerner use gumption to mean common sense. I suppose that the word came to America via Scotch-Irish immigration, or invasion, as some people like to say these days.
A lot of Scotch-Irish move west, to Appalachia and what is now called the South.
Gumption is certainly a Scots word, though via Old Norse rather than Gaelic, and it has migrated southwards. It is believed to be connected with goam (an old Scots word also from Norse = to pay heed; and gumption was sometimes spelled gumsheon and various other pee-less forms) which has also given rise to "gormless" and, indeed, when I was little, gormless was always used instead of the derived but uncommon form of gumption, i.e. gumptionless. Gormless (lack of native wit) was much worse than stupid (lack of education).
I suspect "common sense" mean something different to a rationalist/logician than it does to humbler folk, so you may understand it better as "native wit." Maybe "horse sense" captures it for an American, but I am on treacherous ground there.
Typical, daily uses when I was little were things like:
"You haven't got the gumption you were born with."
"You need to show a bit more gumption."
"Haven't you got any more gumption than that?"
"He's got nae gumption."
The earliest example I know in literature (early 18th century) is from the great poet Allan Ramsay: "Tis sma Presumption To say they're but unlearned Clarks, And want the Gumption." Note the proper pronunciation of clerk
Somebody should have told Mr Webster.
In other words, rather than an attribute such as resourcefulness acquired by training or superior intellect, it was/is something given by Nature to everyone. A man's a man for a' that. Rank is but the guinea's stamp. Etc. etc.
Gormless people choose not to use Nature's gift. But those who choose to refine their native wit can be very approvingly said to be using their gumption. And that is often linked with self confidence or "can do" attitude, though not necessarily approvingly. There was therefore once a form gumptious, but that has now been replaced by bumptious.
Let me make an admittedly bumptious attempt to bring this back on topic. Whenever there is a discussion about word meanings, there is almost always some patronising comment eventually about language evolving, and implied references to dinosaurs. It's not just language, of course, it occurs in almost every aspect of life. I was watching the Ken Burns (the GREAT Ken Burns!) documentary on Country Music over the holidays. There was someone there talking about how country music was evolving into countrypolitan. That was a new term to me, and if it hasn't stuck I suppose that shows that not all evolutionary paths lead somewhere. But the speaker was mainly making the point that some people feared not change but change that was too much or too fast, to the extent that country music was being "obliterated."
Good word. I had a vivid example of the phenomenon myself not long. I went in a London Apple shop not long ago. A personable young man approached, asking if he could help me. I could tell from his accent that he was from my home town. I therefore chose to address in a friendly manner, by using dialect. He just gaped, and then said: "You talk just like my grannie..... And I can't understand her either."
Thanks to the BBC (and Hollywood), language has "evolved" to the extent that in just two generations a young man can't communicate with his grandmother. I find that sad. That's a form of obliteration. (It's worldwide, of course. I read a lot about dialects. My main Christmas present was a tome on German dialects, which I sense are on the endangered species list.)
Too much change, too fast? Revolution instead of evolution? I do wonder whether Yi Se-tol had that feeling, too. He's at an age where you start to think about anchor points in your own life, and watching lemmings rush over the cliff edge is not really much fun when you have children of your own and you want to avoid letting them become lemmings. Not a hope, of course ...