Ring of Fire is Johnny Cash biggest hit. It solidified his career.
It was also a hit for Alan Jackson.
It is a song about pain and temptation. The itch a man or woman can’t scratch.
Oh the pain of burning forever for your sins.
Was Johnny aware of how intense it really is? This gives a new perspective of the song. Affairs often lead to pregnancy.
The song was written in 1963 by June Carter, who would marry Johnny in, I think, 1968. She had 3 children, including one with Johnny, and so may have been familiar with the pregnancy “ring of fire,” though I know of nothing to suggest it influenced the writing of the song. What Johnny may have known about is also likely unknown and at this point, unknowable.I can say that Johnny and his estate have often been asked if the song could be used in advertising for hemorrhoid preparations, and they have steadfastly refused.
Ring of Fire was supposed to be a big hit for June’s sister Anita Carter. But her version didn’t get much air play. Not sure why. It’s on youtube and sounds pretty good. But lacks the edgy conviction that Cash delivers.
That said, Johnny and June did allow the advertising agency where I worked, at that time, to use the song (and Johnny’s recording of it) for an Applebee’s ad, and Johnny even recorded the verbal voiceover about the promotion for it.
My understanding is that Merle Kilgore, who was June’s co-writer on the song, would have happily licensed it for use by Preparation H, but June vetoed that. 
My WAG would be that it was a reference to an old-timey circus-style ring of fire that animals or human circus performers would jump through, used as a general metaphor for getting into a dangerous situation. Listeners of the time would understand the base reference.
ETA: sorta kinda ninja’d by @kenobi_65, as their video link shows a literal fire ring, though not specifically circus-related.
Given that men weren’t expected to know much about woman’s health or anatomy at that time, I’d guess that Johnny Cash wasn’t aware of the use of the expression to describe part of the process of giving birth.
NB: It’s a great song, btw
Over men and horses hoops and garters
Lastly through a hogshead of real fire!
In his way Mr. C. will challenge the world!
Similarly, was the song “Fever” by Peggy Lee about coronaviruses? Was she trying to warn us?
Since Boogie Fever manifests similar symptoms, many people overlook that it is a far more dangerous malady (and melody as well).
I’m gonna have to rethink lots of songs now.
I could have caught the rockin’ pneumonia and the boogie woogie flu, but I had my shots. So now I just like easy listening. mmmmMantovani!
I always thought it sounded like a preacher talking about a vision of hell.
Apparently he wasn’t too happy about its use in another ad.
I always pictured the ring as horizontal, encircling and entrapping the narrator with no escape. It’s not at all like a circus ring of fire, that you jump through once and then it’s done and behind you.
I heard the song used in an ad for Panda Express, except I think it was in Mandarin.
oh the pain. Been there myself.
Yup – that ad came out last year. It’s very similar to the ad that we did for Applebee’s, twenty years ago. When I first saw the Panda Express ad, I sent the Youtube link to the art director with whom I’d worked on that original Applebee’s campaign (and who got to meet Johnny when we produced the ad), jokingly saying, “we’ve been ripped off! They owe us royalties!” 
https://www.youtube.com/watch?v=0S_TqQk5BSY
Ditto, seems quite clear the singer falls “into” a ring of fire.
And there’s really no bottom. It’s just infinitely deep, an impenetrable ring, a veritable hell. No escape ever.
Sounds like marriage to me.
Johnny Cash’s first wife, Vivian, tells a different tale in her autobiography.
From Wikipedia:
"One day in early 1963, while gardening in the yard, Johnny told me about a song he had just written (…). ‘I’m gonna give June half credit on a song I just wrote,’ Johnny said. ‘It’s called “Ring of Fire.”’ ‘Why?’ I asked, wiping dirt from my hands. The mere mention of her name annoyed me. I was sick of hearing about her. ‘She needs the money,’ he said, avoiding my stare. (…) Vivian Cash also states: “To this day, it confounds me to hear the elaborate details June told of writing that song for Johnny. She didn’t write that song any more than I did. The truth is, Johnny wrote that song, while pilled up and drunk, about a certain private female body part. All those years of her claiming she wrote it herself, and she probably never knew what the song was really about.”
She had me believing until this point.
It burns burns burns! That’s not a good thing! Though, they have drugs to fix that.
Nothing I’d write a song about, unless it was called "Why Does It Hurt When I Pee?