What we do know is that it did not exist in print or any other media from before that point. And since it makes absolutely zero sense, as it’s been described, that’s further proof it’s made up. Even if a casket handle was a huckle, as has been claimed, it’s also still a handle, right?
And you wouldn’t call anyone a “handle bearer”, would you? That’s exactly what it would mean.

You bear a load or a weight, not the handle of the load/weight.

So that whole thing was invented on the internet, and exists nowhere else.

Oh, and one more source for “I’m your huckleberry”: The old 1950’s TV show “Yancy Derringer.” First episode (its on youtube), near the end, Yancy tells a man “I guess I’m your huckleberry” after confirming what the man wanted him to do.

It really wasn’t, though. The idiom I’m your huckleberry existed in print well before Mark Twain published his books.
It’s been speculated that Huckleberry Finn’s name came from that old saying…which makes sense, since if anyone was ever your huckleberry, it was Huck Finn.