OK so I am reading a novel by Tana French. She is Irish. My second police procedural by her. In the Woods was my first and I LOVED it. In this new one Broken Harbor, she uses this marvelous contraction. The rookie says to his supervisor, “I’m here amn’t I?” Such a logical contraction. “I’m here am I not?” I think we would say, “I’m here aren’t I?” But it wouldn’t be right, would it? “I’m here are I not?”

Quinion has a great article on this. I had no idea!

First off, amn’t (which is short for am not) may be unfamiliar to most of us, but it isn’t entirely unknown, though it’s almost exclusively found in the inverted form amn’t I. It’s used in Scotland and Ireland, for example. Why the rest of us don’t is a result of shifts in pronunciation that were associated with a loss of favour generations ago.

My wife (Dublin-born middle class) says “amn’t I” sometimes, though only as a joking imitation of Irish country folk, she insists. I see that Quinion suggests most brands of English don’t say “amn’t” because

speakers disliked putting an m and an n together in one syllable

- Irish/Scots Gaelic does not have that problem (eg the Irish for “women” is mna) and therefore, perhaps, people in Ireland and Scotland lacked that “don’t like pronouncing ‘m’ and ‘n’ together” incentive to stop saying “amn’t” that the rest of us had.

I’ve seen it stated, I don’t know on what authority, that ain’t derives from amn’t. It would seem logical, especially as I have seen the spelling an’t used in dialogue, and an’t is exactly what you get if you elide the tricky M sound from amn’t.

The OED says that ain’t is a variant of hain’t, or have not, has not. That’s much simpler and more logical since ain’t generally isn’t used where am not would be.

As for amn’t, the OED says:

With enclitic negative particle. (i.) 16 amt, 16–17 (19– U.S. (nonstandard)) amn’t; Eng. regional (west midl. and north.) 18 ammot (Yorks.), 18– amma (Shropshire), 18– ammad (Shropshire), 18– amna, 18– amnad (Shropshire), 18– amn’t, 18– am’t, 19– amment, 19– ammet, 19– amno (north-west. midl.); Sc. 18 amnin, 18 ym-n’, 19– amnae, 19– amn’t; Irish English 18 am’n’t, 18 imin’t (north.), 19– amn’t.

Followed by quotes ranging from 1658 to 2003.

Irish/Scots Gaelic does not have that problem (eg the Irish for “women” is mna)

Well, in western dialects like the Connemara Irish I studied, /n/ changes to /r/ in that context (so that mná is pronounced /mra:/), so that isn’t a universal explanation.

I don’t really have much to offer other than wild speculation, but, here it is FWIW:

It strikes me that “ain’t” is a rather busy contraction: it’s used for am not, is not, are not, and have not (at least, by those who use it at all).  For example, in the usage “I ain’t got a clue” ain’t seems to mean “have not” (at least, I can’t think of another way to make it “work").  In something like, “if it ain’t broke, don’t fix it,” it stands in for “isn’t”.  In, “hey, i ain’t deaf, it means “am not” (amn’t? An’t?), and it means something similar (with some “cheating” as to word placement) in, “I’m here, ain’t I?” (am I not?). (or perhaps “am not I”, although the latter sounds very odd to my ear, but, then again, many things that sound odd to me either were or are standard usage).

To take the wag further, perhaps ain’t was used as a variation on “hain’t” at some point by some people, and as a variation on “an’t” (itself a variation on amn’t) at some (other?) time by some (other?) people. At some point, the two usages became conflated, and various english speakers used ain’t for both haven’t and an’t, with isn’t and aren’t joining the party at some point. A word with such a confusing ancestry and surplusage of usages was bound to draw the wrath of the prescriptiviists, as, indeed, ain’t did.

A final wag: perhaps language hat’s observation regarding how “m” is pronounced like “r” in some dialects helps explain how “aren’t” ended up pairing up with “I” in “aren’t I”: aren’t may be an alternate pronounciation of “amn’t”. (the quinion article seems to hint at this).  It may also have played a role in the overlap in usage between ain’t, amn’t, and aren’t.  (I also suspect, but don’t really know, that ain’t and aren’t sound more similar in some dialects than others, which may have been yet another source of overlap/conflation in usage between ain’t and aren’t).

“‘When I make a word do a lot of work like that,’ said Humpty Dumpty, ‘I always pay it extra’.”

Yes, the use of ain’t is definitely more broad than OED’s cites suggest. Examples such as the following are common in some registers of English:

He ain’t coming, she ain’t there, ain’t you ready yet?

In other words ain’t can also supply the place of is not, are not, am not, although you wouldn’t know that from the entry or cites in OED.

That ain’t is now used with second and third person subjects isn’t strong evidence that it did not derive from amn’t.

BTW I’ve only once encountered amn’t in the wild, used by a lass from Galway. I thought she might have been doing it for a laugh.

I think we would say, “I’m here aren’t I?” But it wouldn’t be right, would it? “I’m here are I not?”

Strange though it seems, “Aren’t I” is accepted very widely, even though “I aren’t” isn’t.

I’m sure it is derived from hain’t for haven’t, hasn’t. But it’s also far from unlikely that the old written contraction a’n’t for am not would have seamlessly melded in with the existing ain’t leaving the latter form to stand for the whole shooting match of have not, has not, am not, is not, etc (on both sides of the Atlantic).

Ain’t she sweet
See her walking down the street
Well I ask you very confidentially
Ain’t she sweet

Milton Agee/Jack Yellen 1927

Mmmm, but then, there’s the West Country ”baint”, meaning am/are not, and presumably connected to the West Country use of “be” as the all-purpose present indicative (Oi be, ee be, we be and so on), so that “be not” ?became? (I’m guessing) “baint”, presumably because that’s easier than saying “be-n’t”.