When did "the rainbow bridge" become a popular metaphor for pet deaths?

Pretty much what I’m asking in the title:

As an adult, I’ve noticed that many people will refer to “the rainbow bridge” when talking about pets that have died.

I don’t remember this concept from when I was a kid (except Bifrost, because I was that kind of geeky kid), but of course I could have just not run across it.

Where did the concept of “the rainbow bridge” as a metaphor for dead pets come from? Am I right that it’s a relatively recent (as in, '90s or later) concept? Is it mostly US-centric, or international, or what?

Wikipedia suggests that it started to become current on the Internet in the early 1990s.

For what it’s worth, I’m a dog owner who knows lots of other dog owners, and I had never heard of this until I saw this thread. I have lived in Ireland and Australia. I’m guessing this is mainly or exclusively a US thing.

I’ve never heard it.

Another USAer here. Never heard of it, and I’ve had lots of pets die over the past 50 years.

I’ve heard of the Rainbow Bridge for a long as I’ve been online, since the early 2000s. I’ve also received sympathy cards referencing the Rainbow Bridge from veterinarians after the loss of a dog.

I first heard the term around 1995.

Never heard it.

https://www.reference.com/art-literature/wrote-rainbow-bridge-poem-827b568f9a94ead3

According to this, three people claim authorship of the Rainbow Bridge poem.

I first came across the poem in 2006 after the death of my beloved Scottie. I don’t care, really, who wrote it. I am, however, very grateful it was written.

I first heard of it on the Internet circa 1999. Somehow even my Mum has heard of it.

It’s exactly the kind of thing that people’s Mums will have heard of!

Just a data point – when I was a kid growing up in southern Ontario, the “Rainbow bridge” was (and still is) the Canada/USA bridge that gives you a view of the Niagara Gorge and Niagara Falls. It never occurred to us to fling dead pets off of it.

I’m hoping you jest. The bridge is where pets meet their owners when they too pass. No flinging.

I remember reading the Rainbow Bridge poem in a Dear Abby column, probably in the late 1980s.

The only Rainbow Bridge I have heard of is in Utah.

That’s exactly where I first encountered it but it would have been in the early 90s to the best of my recollection. She tended to repeat herself a lot though.

We recently got a card from the vet oncologist using that phrase after our Lab died. I’m pretty sentimental about canines but that one produced an eyeroll.

Mrs. J. liked it though.

Mostly these days I see it on Facebook. I find it nauseating personally, but understand why it brings people comfort.

Freaking ridiculous.

It’s been a metaphor for the junction between Earth and the gods for a few thousand years.

Oddly, the bridge between Earth and the realm of the dead is something else. Not a rainbow or multi-colored but covered in gold.

So, if you’re Norse, you and your pets end up in different places unless you die in battle.

I first came across it in the late '00s and have seen it a lot since I frequent dog related forums/am part of dog related FB groups.