The song "Brown Eyed Girl", although rumored to be about a black woman that Van Morrison was in love with, is really about anal sex. The original title of the song was not "Black Skinned Girl", but rather "Brown Eye, Girl", referring to, well, the brown eye, the anus, the cornhole, the shit chute, the pooper. However, in 1967, although the Sexual Revolution was peaking, the recording industry was not ready for a song that was so explicitly about anal sex. Here, I break down the actual meaning of the lyrics.

Hey where did we go,
Days when the rains came

This is a question that every man asks when his woman is bleeding, or "when the rains come", and, to date, there are very few answers. Since it's a trivial matter to have anal sex without getting any menstrual blood on you, Van Morrison is obviously talking about he and his ladies sexual escapades.

Down in the hollow,
Playin' a new game,

If "the hollow" isn't a phrase that means "the anal cavity", then we might as well just give up on the English language. As for "playin' a new game", that should be obvious to anyone who's ever tried to open the Backdoor to Paradise. Anal sex isn't something that you just jump into with a woman, unless she's a total whore, you need to work up to it slowly. It's a new game, because only now is she willing to give up the bung.

Laughing and a running hey, hey
Skipping and a jumping

Among the gay community, amyl butyrate and nitrous are commonly used to make the initial pain of anal sex less than it otherwise would be. If you've ever done nitrous, you know that it makes you giggle like a maniac. Obviously, caring for this woman, he wanted to let her prepare appropriately for her first ass fucking.

In the misty morning fog with
Our hearts a thumpin' and you
My brown eyed girl,
You my brown eyed girl.

When their brains were fully fuzzed by the drugs, and the tension building, they finally decided to go for it. She's willing to take on in the rear for him, so she is in fact his "Brown Eye Girl".

Whatever happened
To Tuesday and so slow
Going down the old mine
With a transistor radio

The second verse is set some time after the initial ode to the butt. They've gotten into a habit of having anal sex. It's no longer just an event that happens on Tuesdays, and he no longer has to enter her ass slowly. Now, because it's been stretched out, the "old mine" has to be entered with full cave gear, so he knows how to get back. After prolonged anal pounding, his woman has a loose ass, and he's displeased.

Standing in the sunlight laughing,
Hiding behind a rainbow's wall,

Among scholars, the meaning of "sunlight" is under much dispute. I believe that it symbolizes the love he has for her still, despite her less than teenage-girl tight anus. At the same time, he can't tolerate being with her, because sex is no longer enjoyable. To avoid hurting her feelings, he claims that he's gay, and "hides behind the rainbow wall".

Slipping and sliding
All along the water fall, with you

The waterfall is her distended anal cavity, which is probably pretty leaky at this point, and he slips and slides along it because it's so loose, he can't get any friction going.

So hard to find my way,
Now that I'm all on my own.

He still wants to poke girls anal, but it's more difficult to find someone that's willing now that he no longer has his brown eye girl.

I saw you just the other day,
My how you have grown,

Damn bitch, you got fat!

Cast my memory back there, Lord
Sometime I'm overcome thinking 'bout
Making love in the green grass
Behind the stadium with you

This is a two parter. First, he wants to remember her as she used to be, not as the fat pig that she is now. Secondly, he masturbates thinking about the sex that they had, and misses it.

That's it. Brown Eyed Girl is about anal sex, and Van Morrison loves to fuck girls in the ass.