The easy answer is that Aaron is meant to be pronounced:
ah’ha’RONE
Three syllables?? No way! Can’t make me pronounce it that way!
I’m from Philly (originally) and to me Aaron, Erin, and baron all have distinct first syllables and heron is the same as Erin. Baron is pronounced with a short vowel that is similar to the vowel of back (but colored by the following “r”), while Erin is pronounced like error and Aaron with a long vowel like that of air.
My wife pronounces all of Mary, marry, merry, and Murray distinctly. I pronounce the first three distinctly, but merry and Murray the same. So it goes.
As for some dialects being vowel deprived, I read in some phonetic book once that various dialects of English have between 22 and 24 vowels and, while I have never counted, that doesn’t sound like vowel-deprived to me. Especially given that many languages have only 5 vowels and there are few with only 3.
One other thing. In my dialect, sad and bad do not rhyme. Bad, mad, and glad are given tense vowels and all other -ad words are lax. On the other hand, man and ran don’t rhyme either. But in this case, there are three, ran, can (modal only), and began that are lax and all others including the noun and verb can are tense.
There’s a certain amount of hair-splitting going on here about what truly qualifies as a rhyme – last syllable, all syllables, stressed syllable. I’m pretty sure the OP meant that the words sound similar throughout, to the point of being indistinguishable to the ear, so that’s how I’ve interpreted it.
If I was attempting to pronounce someone’s name from a written text I’d say it the way I was used to saying it, and then if the person said “actually it’s pronounced …” I’d be happy to change (if only for their case), so the correct pronunciation is their pronunciation, not mine.
Having said that, maybe I should try to clarify my previous comment? It’s not easy to show pronunciation here, and comparisons with other words assume that you’d recognise my pronunciation of those other words too right? By the way, I come from Liverpool in the north of England originally, so pay no heed to the London location.
To me the words sound like this:
Erin – first syllable is stressed and sounds like the first syllable of “error”, second syllable is weaker but sounds like “opposite of out”.
heron – first syllable sounds the same as Erin, second syllable is a schwa quite like “un”.
Aaron – first syllable sounds like “air” (!), second syllable like heron.
baron – first syllable is difficult to explain. It’s like “cat”, but a northern English pronunciation of cat, with less of an “e” component than a southern English one such as Hugh Grant’s. Second syllable sounds like Aaron and heron.
Mary – first syllable contains the “air” sound and is stressed, second syllable is a weak “ee”.
marry – first syllable is like baron, second like Mary.
merry – first syllable like Erin, second like Mary and marry.
father – first syllable is a long “aah”, as in the sheep’s noise others have mentioned, second is a schwa (I don’t pronounce the “r” at all).
bother – first syllable is much shorter and doesn’t include any “a” component (like a cork coming out of a bottle), second syllable like father.
Dawn – difficult again, but it’s long (a bit like “door” or “broad”).
Don – short, like the first syllable of bother.
I hope this helps, Algernon.
The only way I would pronounce the last syllable of Erin as /in/ rather than with schwa is if I were singing “Come Back to Erin, Mavourneen, Mavourneen.” Because in song you’re supposed to articulate syllables more clearly than in speech. At least they taught that in chorus when I was growing up. Kurt Cobain must have skipped class that day. Song can do funny things to syllables, sometimes. I remember being taught to sing “O Come O Come, Emmanuel,” in which we had to pronounce “Israel” as iz-rye-elle. The name never had any “rye” or any other grain in it otherwise, only in that song.
I agree with you on all of them…right up until the last pair. Don and Dawn sound alike here, so much so that everyone was in shock when my last hall director was talking about her SO the day we met her…we thought she meant she was living with a D-o-n, but then we realized she said “she” so she was living with a D-a-w-n 
For the record, AHunter3’s tot and taught sound the same to me as well. But then, many of us up here don’t fully pronounce the last syllable in words like drawer and borrower so I’m not claiming that how I say things is the correct way.
However, when my friend Aarin(her parents’ creative spelling of “Erin”) was dating Aaron, we could almost always tell who was being spoken about- as long as the speaker realized how Aarin’s name was pronounced.
Just wanted to mention that I went to college in Arkansas with a girl named Dawn Johnson. Pronounced exactly like the name of the actor.
Upon reopening this thread, I realize that my last post made me sound like a complete jerk.
What I meant, of course, is that given the original Hebrew spelling of Aaron (aleph-heh-resh-nun if I remeber correctly), one might be disposed to pronounce it as ah’hah’RONE or even ah’RONE.
But clearly there is no one correct way and if you tell me that your name is spelled Aaron but pronounced RAY’mund’LUX’you’ree’YACH’it, then that’s how I’ll pronounce it.
I’m an Erin IRL. I pronounce Aaron slightly different than my own name.As long as you don’t call me Erwin, which happens more than you might think, or Urine, as an old lady who used to work for my dad did, I don’t care.
No that’s what I thought too,:smack: and I assumed that Aaron & Erin were morning DJs somewhere. 
This thread has recently been linked to by the radio show A Way With Words, so I am performing voodoo in anticipation of a raising.
Aaron and Erin are certainly different, and Erin doesn’t sound like heron either. I’m not sure how you’re saying those last two.
For me, I pronounce them differently.
Aaron: Air-uhn
Erin: Air-ihn
Zombie: zahm-bee
Sumbee: suhm-bee
I share the marry-Mary-merry merger, so all three words, and the two names you asked about, are exactly identical homophones. I’m a native of northeast Ohio and speak central Inland Northern American. In this case, the isogloss separating the merged from unmerged areas follows the Allegheny Front in western Pennsylvania.
No, you are not… 
i have a question for those who claim they’re homophones. i understanding pronouncing it the same, but deep down, in the back of your head, don’t you have an inkling that “properly” they’re not supposed to sound the same?
like if you were to imagine a news anchor say those words, do you hear them say it as you do, or are you aware that there is a different way of pronouncing those words?
for example, i grew up in the south and have a bit of a drawl to my speech - so that drawer is pronounced like door with an ‘r’ after that d. however, i do KNOW that it’s supposed to sound liker draw-er, but i just can’t bring myself to say it as such. wondering if you midwesterners “know” just like i do but just aren’t bothering, or you really can’t hear the difference between aaron and erin, and mary/merry.
Mary, marry, and merry are homophones to me and I’ve never understood how anyone could even attempt to pronounce them differently. Until reading this thread, and noticing the slightest difference in the vowel sound in Aaron and Erin, I thought the OP was bizarre. But in everyday life I wouldn’t distinguish them and I wouldn’t expect anyone else to do so. And baron and heron absolutely rhyme and I still can’t figure out what the difference is even theoretically.
In my native accent, they could be pronounced differently, but normally aren’t. In other words, I’d say “Aaa-ron,” with the same “a” as in “cat,” if I really wanted to emphasize the difference between the two names, but in everyday speech it would normally get slurred to “Er-on,” with the same “er” as in “merry.” (Which isn’t exactly homophonic with “marry” if you really enunciate, but it is in everyday speech. “Mary,” on the other hand, is quite different; it has the same vowel sound as “air.”)
Similarly, I would pronounce “Don” as “Dahn” if I were really trying to emphasize that he’s a different person from “Dawn,” but most of the time I wouldn’t bother.
Never mind, joke already made repeatedly.
I have friends named Aaron and Erin and they dated for a while. I never heard the slightest difference in the pronunciation of their names. We’re all from Ohio.
Since he was our friend first we called him Aaron and her ‘not you’
Baron and heron sound the same too.
When looking at the named I do think they should be pronounced differently but I can’t even imagine how everyone else is saying them.