Apparently not to Merriam-Webster, which says it’s from “are not” (as does the OED).
You’re giving up without being able to respond to my last argument. Whatever you mean by it, you know what that looks like, right? Generous folks might not assume that you’re leaving because you can’t respond, but I’m going with Occam’s on this one.
It’s not the same argument at all. I pointed out that writing developed as a reflection of speech, and thus that it’s fruitless (and logically incorrect) to use it as a source of prescriptive advice for pronunciation. You, incidentally, have yet to provide any argument to explain why “nuclear” may only have one pronunciation, while other words have multiple accepted pronunciations.
You also fail to provide an argument to demonstrate why past pronunciations of a word are necessarily better than current ones - since the pronunciation of a word at some point in history was just the consensus of the time on how the word was pronounced, why is that past consensus somehow superior to the present one? Go to my previous post to see examples that demonstrate that usage and word forms in the past do not agree very well with current prescriptive norms, and tell me why prescriptivists look to the past when it supports their claims but don’t do so when it doesn’t.
The origin of the contraction “ain’t” is “am not.” It’s definitely true that usage has changed; “ain’t” can be the negative form of any present tense form of “be”.
“Ain’t” descended from “an’t”, which was present at least in the 17th century. “An’t” was largely used at that time to mean “am not”, but there is a citation existing even from back then in which it was used for “are not”. I would venture that the phonological similarity of “aren’t” and “an’t” promoted a merger of sorts. “Ain’t” basically reflects a change of spelling, perhaps or perhaps not reflecting a change in the pronunciation of the vowel. When prescriptivism came into the fore in the 19th century, “ain’t” was condemned, specifically as a low-class speech mannerism, and on grounds that it was being used more generally than “am not”.
I’m not sure what you’re getting at here, anyway - “ain’t” really is, in my opinion, a very useful word and it’s sad that it is now unacceptable in standard English. How should Sojourner Truth’s famous speech be renamed? Using the stuffy and awkward “Am I not a woman?” Or with the awkward (and clearly illogical, which should give you prescriptive types reason to salivate) “Aren’t I a woman?”
It’s easy to see how “ain’t” would be further generalized as a negative of “to be”. Once “an’t” was established meaning both “am not” and “are not”, the only remaining present tense form of “be” that couldn’t be negated as “ain’t” was “isn’t”. A regularization occuring in these circumstances is not at all surprising, which is my best guess for how “ain’t” became so ubiquitous. If you think it shouldn’t be so, explain why.
The ultimate origin of it is rather unanswerable, since (as I mentioned in my above post) both words ended up subsumed under the one contraction. I’d be curious to see what the OED says, since they provide citations, but the oldest ones I’m aware of were used as a contraction of “am not”. I’ll reserve judgment for the present, but Merriam-Webster have not supported their claim, and it’s pretty firmly a contradiction to the (fully cited) explorations I’ve read on the topic.
Excalibre is right, sez pretty much every linguist out there. I’ll trust physicists to tell me how many electrons are released in a nuclear reaction, but I’ll trust linguists to tell me how I can pronounce “nuclear reaction.”
Daniel
I convinced my 6th grade teacher to stop spelling “imperfect” “inperfect”. IANMTU.
Excalibre
You, incidentally, have yet to provide any argument to explain why “nuclear” may only have one pronunciation, while other words have multiple accepted pronunciations.
Most words have only one pronunciation. According to your “logic” they can be pronounced however one pleases huh?
Why do I get sucked into these things, 22 years old fer chris’ sake 
IANMTU?
I am not a magnificent tofu user?
I am not a member of a teacher’s union?
I am not masturbating till tUesday?
Sorry, I can’t puzzle that one out at all.
I am not my teacher’s uncle.
Daniel
If anyone nose moronspeak, thx u!
Daniel
Left hand of dorkness
“Nu-clee-ur” or “nyoo-clee-ur” but not “noo-cyu-lur”
Excellent! Where’d you get your degree in linguistics?
Daniel
Really?
You own a dictionary?
I opened to a random page of the AHD. More than two thirds of the words on the page (3rd edition, pg. 1276) have multiple pronunciations listed. Do you take a brave stance also that your preferred pronunciation of “apricot” is superior to the utter debasement of the language inherent in that other pronunciation? Why is nuclear different then all these other words? What’s superior about one pronunciation over another? What makes a pronunciation correct or incorrect? I say anything in common use is, by definition, correct. Native speakers of English frequently pronounce “forte” with two syllables (in fact, they do so an overwhelming majority of the time). What makes your pronunciation (based upon incorrect French) better than theirs? If a large number of native speakers use a particular pronunciation, it only makes sense to me to say that it’s “correct”. To say otherwise seems, to me, about the equivalent of an anthropologist deciding that the chimpanzees she’s observing are mating “wrong”.
I say that if there is to be a legitimate prescription of language usage, it should be based upon a logical examination of the language, and thus a systematic explanation of what is “right” and “wrong” is necessary. Couching language rules in appeals to a nebulous authority - saying just that “This is how it’s supposed to be pronounced” - is unsatisfactory. Thus, a set of principles must be given to justify claims that one common usage is right while another is wrong. It’s a large issue, but if you wish to argue the basic point, I’m open to it.
Where did I say that? Where did I even suggest that? My point has consistently been that common usage is the only arbiter of correctness. “However one pleases” is a vastly different creature than “how a word is commonly pronounced”. You’re setting up a straw man here. You can do better than that, I hope.
This has been explained a number of times on this board by people better and smarter than me so, really, it’s a shame you missed it. Anyway, the “near” in “near miss” illustrates the proximity of one object to another. When an object experiences a near miss, it just means that whatever other object missed them happened to do so by a very small margin. The objects were near each other but avoided collision.
Ever notice how if you say (or write or type) a word several times in a short period, it ceases to have any meaning at all?
Why?
I mean, we don’t just accept a person’s opinion without any justification for it in any other area. Why should we do so with language usage?
I’ve used a different standard in the past, and I’m interested in your take on it: I’ve said the only arbiter of usefulness (not correctness) is whether the speaker has successfully communicated the idea he or she intends to communicate to the intended audience.
For the most part, our two standards coincide. However, it seems as if your standard would consider someone speaking in Piglatin to be “incorrect,” since it doesn’t match common usage; my standard would count it as useful only if the audience understood it (or if the intended audience was supposed to be baffled and was baffled).
Since language derives a lot of its utility from its shared nature, and since its shared nature allows people to communicate ideas effectively, our standards overlap a lot. I just find utility ot be a better measure of language than correctness.
Daniel
Remember that in French the adjective and the subject must have gender agreement. So if the word is feminine, the spelling would be “forte.” Also, if the next word starts with a vowel, the final /e/ would be present so that the speaker would voice the /t./
In French class it was taught as the phrase “forte en” meaning “strong in/at.” Mme Hartman gave the same argument and it made perfect sense: Forte=strong forté=loud.
And I am forte en playing fortés on my F horn. Sforzandos, even. 
I’ll take ‘wrong answers’ for $1,000. 
No need to venture so far. Quite a few inhabit the Straight Dope.
**Exgineer ** (forgive me if you’re a Repug after all) spells out what I take to be the liberal position pithily.
Well, the modern standard form would be “Aren’t I a woman?” There’s nothing unusual about the use of unusual forms for the sake of euphony (which, indeed, is what gave rise to “ain’t”). For example, in French, “je peux” (I can) turns into “puis-je” as a question, where “puis” is an archaic form of the verb.
I wonder if anyone’s mentioned “Here, here!” yet.
It’s “Hear, hear!” It means “listen to this!” and is a direct translation of the archaic French Oyez, oyez!