What influenced people to start using "I'm good" in answer to "How are you?" and in other contexts?
There are many posts on this site about the appropriate responses to the question "How are you?" and there are many different opinions about which responses should be used. My intention is not to bring that question up here.
My question is about the evolution of the expression "I'm good". I hear it used in two ways all the time. One is in answer to the question "How are you?"
The other way it's used is to mean, "No thanks, I have enough," or "I'm all set here." For example: "Would you like more ice cream?" "No thanks. I'm good." Or this: "Did everybody understand my explanation?" "Yes, I'm good." It's also used in the same way in questions. A waiter might arrive at a table and say, "Are you good?" to people who appear to have finished eating, as a way of asking whether it's OK to take away their plates.
We moved from the United States to France in 1988 and stayed there until 2002, when we returned. Before we left, I never, ever heard anyone say "I am good" in either of those two contexts. When we came back, the expression was everywhere. So I've always assumed that it emerged during the 1990s or, at the latest, around the year 2000. I've also always (perhaps erroneously) assumed that both types of usage evolved around the same time. Many of the posts on this site refer to "I'm good" as an expression used only in American English, but recently I have heard it used by many speakers of British English as well.
I've checked various sources to find the expression's origin. There are a few ideas about it here, here, and here. In the last of the sites I've referenced (wiktionary.org), there are people in a chat room who agree roughly with my estimate of when the expression entered common usage, and one of them suggests that it comes from language used by poker players.
I'm very interested to know if anyone has found more authoritative information about the origin and evolution of the expression, as used in the ways I've described.
It could be a kind of illogical carry over from another language. This is a colloquialism that could have started with bilingual/illiterate populations. There are presumably many languages in which the word for "The state of (an object or person) being in fine condition (i.e. "good")", overlaps with the word that can also describe "The state of a person's mood, which yields nonmaleficence/positive social behavior".
This is also true in English if for example you "fill in the blank" and assume that good is short for "I am in good shape". Shortened to simply "I'm good". which is incorrect because it actually means "I am benevolent/I am well-behaved". The relationship between the words is not obvious, but it can make sense if a few tweaks are made to the sentence.
The phrase "I am in good shape" basically establishes this relationship between the words "fine/well" and "good", by materializing an abstract concept which is "mood" as a malleable physical ["geometrically-shaped"] object which can be thought of as "damaged/altered/broken" when a person is "feeling down", or be "well/fine" i.e. in an intact/good/aesthetically pleasing condition when it a person is psychiatrically healthy.
See Spanish for example, "Bien" (well/fine) versus "Bueno" (good). In this language, the words resemble each other more closely. It is easy to assume that this is also the case in many other languages, and as you know, languages "evolve" as a result of people speaking incorrectly.
So for a bilingual person, it is "logical" because not all English 'word-usage customs' are taken into account, making it illogical for someone who knows the language to a better degree or is simply more concerned with following its rules.
The implied "etymological assumption" is the following: "Benevolence/tidiness/stability (good) is to happiness (fine/well), as maleficence/evil/untidiness/instability (bad) is to unhappiness (not fine/unwell)".
Regarding the "Ice cream" example, the answer is simply indicating that a person is emotionally content or in a state of complacency in response to an outcome. So they are not actually answering your question quantitatively (as expected). Instead, they are conveying other information, which in turn, only implies the desired answer. I.e. If a person is happy, then you can safely assume they are satisfied with that specific amount of ice-cream.
The 'conjugate' expression (which does not exist, and should not exist) would be the following: "Would you like more ice-cream?" --> "I am feeling evil/antisocial" or "I am bad" wherein, "evil/bad" represents an ill-intended (hence 'structurally unsound'/unstable) state of mind, which in turn would convey that the person "is unhappy and therefore does want more ice-cream".
Sources = My dyslexia.
My answer is too long... "My bad!"... (mistake:mischief/misbehavior:bad)
Also consider the following: Fine and good, may also both overlap, and be misused in other contexts, as they can both also refer to gustatory appeal "Taste", and even auditory appeal, (not just visual appeal/condition). E.g. "Fine wine" or "Good wine" "A carefully put-together delicacy, or of high quality".
So in English, (as in many other languages) you can say "She is fine", and it could mean anything from "She is doing well", to "I really wanna hit the hay with her", and everything in between...
So in this case, a positive state of mind is being equated to a high visual appeal, and then, the phrase to depict that figure of speech is being shortened...
Just to add something that hasn't been mentioned yet (I do like @BoozyBeaver's take on carry over from another language), there could also be carry-over from a standing idiom by way of abbreviation. I'm calling it a carry-over because it's not strictly logical but close enough:
How about good to go ? (explained well on the M-W page that turns up upon search there). Being in a state fit to commence something (or carry on), that's very close to a strong meaning and sufficiently close to "I'm fine" while lacking the nuance that comes with it. So, a likely candidate for how carry-over works (though I couldn't formally describe that right now).