Whence comes the association of Leprechauns with rainbows?

Question

In the modern day, leprechauns are usually associated with a highly rigid depiction: wearing green, hat, buckled shoes, red beard, pot of gold at the end of the rainbow.

Some parts of this may come from stereotypes of Irish people (probably the beard and the green clothing to some extent), and some come from folklore. For instance, in Fairy and Folktales of the Irish Peasantry, Yeats quotes a poem by Allingham, which clearly gives us the gold:

This keen miser-fairy hath,

Hid in mountains, woods, and rocks,

Ruin and round-tow'r, cave and rath,

And where the cormorants build; From times of old Guarded by him;

Each of them fill'd

Full to the brim With gold!

The buckles are also mentioned here, although they are silver.

Silver buckles to his hose.

As are some other aspects of the genteel dress.

However, I can't find any mention of a rainbow, and I can't think of any particular reason for it to become associated with Irish fairies of any sort.

What is the origin of the association of leprechauns with rainbows?

Answer 1

What appears to have happened is a 20th Century conflation of two different legends, one involving leprechauns and gold and another involving rainbows and gold.

There is really no evidence associating leprechauns with rainbows before the 20th century. (A different answer quotes a Time magazine article from 1952).

The sole folklore-related Google Books result from the 19th century containing both "rainbow" and "leprechaun" comes from Irish Melodies, a compendium of poems by Thomas Moore, but a look at the actual page is disappointing: the end of one poem mentions a rainbow while a footnote to the next poem mentions a leprechaun. It's just a typographical coincidence.

An 1851 book of Northern mythology talks about pots of gold at the ends of rainbows as coming from Germanic myth:

According to a popular belief in Germany, Denmark, and England, a golden cup or hidden treasure lies where the rainbow apparently touches the ground. This seems a remnant of the belief in Mimir's spring, in which wisdom's golden treasure was concealed.

-- Benjamin Thorpe, Northern Mythology, London, 1851, p. 158

Thorpe refers to Mimir's well, which lies near the Jotunheim end of the rainbow bridge Bifrost. No leprechauns here.

The Tree of Myth, an 1889 book of folklore by Charles de Berard Mills, states:

Children believe at this day that a golden cup or bag of gold lies at the end of a rainbow. The story comes from the ancient sun-myth so widely diffused, of the golden orb sinking into the waters of ocean or stream or lake. In one transformation it was the legend of a golden treasure buried in the Rhine, as we have it in the Niebelungen Lay, then finally, changed as it is in the nursery tale, we see the old myth again.

No leprechauns here, either.

Leprechaun gold is well-hidden and guarded. It doesn't have a rainbow directing the whole world to its location:

If you could only catch the leprechaun at his work and hold him, he would tell you where the crock of gold, his hidden treasure, lies hidden. Nor would it turn into fairy-gold, once found. But the leprechaun is artful and plays shabby tricks sometimes. He was once caught by a peasant, and in return for his release indicated where a crock of gold lay. It was under a spike of ragweed in a thirty-acre field.

-- "Irish Superstitions, Spells, and Charms", Katherine Tynan Hickson, The Outlook , collected in Current Literature, 1895

Notice you don't find the leprechaun's gold just lying around at the end of the rainbow, you have to kidnap the creature and make him tell you where the gold is.

This is a good segue to what appears to be what I think is the point of conflation, which is the 1947 Broadway musical Finian's Rainbow, by E. Y. Harburg and Burton Lane. It was a smash hit that ran for 725 performances, and was later made into a 1968 movie starring Fred Astaire and Petula Clark.

Ever since I was 2, you've been seeing leprechauns (in the cabbage patch) and rainbows over your whiskey jug.

The play revolves around a pot of gold that Finian McLonergan stole from a leprechaun in Ireland, then brought across the Atlantic to Rainbow Valley, Missitucky. He hopes to bury it near Fort Knox in hopes the gold will multiply. But Og the leprechaun follows Finian to America trying to get his gold back.

Notice it's not said the gold was found at the end of the rainbow...instead, Finian brought the gold to the end of the rainbow. Nevertheless the opening number "Look To The Rainbow" uses the rainbow as a metaphor for a dream to be followed. All of the elements swirl together and it looks like that's how this entered popular folklore.

Answer 2

According to Ancient Origins

Leprechauns are now understood to be the fairy tales of the past and fanciful stories to tell when one sees a rainbow.

I'm afraid I can't find anything else either.

It may have been associated after Christianity came to Ireland, the rainbow being associated with the end of the great flood as told in the Genesis, and therefore hope and perhaps luck.

The gold pot could be more easily traced

According to William Butler Yeats, the great wealth of these fairies comes from the "treasure-crocks, buried of old in war-time", which they have uncovered and appropriated. (from Wikipedia)

the 'crocks' being pots.

Combine the pot of riches with a symbol for luck and one comes across a pot of gold at the end of the rainbow.

Due to rainbows being somewhat common, I would imagine the idea being readily adopted and surviving to this day.

Answer 3

I think the answer is that they hide their gold where no one can find it - as an article in Time magazine puts it:

Irish folklore described leprechauns as crotchety, solitary, yet mischievous creatures. They were said to be shoemakers who socked away their profits in pots at the end of rainbows, or scattered them around in mountains, forests, or rocks.

It goes on to say that if you try to steal the lephrechaun's gold, they will try to distract you, because they're misers.