Speaking of rain I saw this rainbow this other day. Although rainbows are a familiar sight, when one appeared all the people around me were quite excited, and I was too.
This got me wondering what rainbows are called in other languages. Is the name a compound, similar to the English rain+bow? On a quick look I found some where it was, and one or two rather different.
German is regen-bogen, evidently cognate with the English. Old English had regnboga, also very close, but it also had scurboga, and recalling that "sc" in Old English was pronounced as "sh" this would be shower-bow, which rather sadly is now lost. I think we shyould bring it back.
In French we have arc-en-ciel, "arc in the sky", so no reference to rain. Italian is arco baleno, which I think means something like "arc-flash", so that's a bit different, but still has the bow theme.
Latin was iris, borrowed from Ancient Greek I think. Iris was personification of the rainbows. Her name may have originally been Wiris, starting with the archaic digamma, a letter lost in later Greek.
Modern Greek has a different word from Ancient Greek and it baffled me at first, ourano toxo. But after some head-scratching I recalled that Uranus was the personification of the sky and toxo means bow (as in toxophilite, one who likes archery, and the word archer must also be related to arcs/bows). So the Greek expresses the same idea as the French arc-en-ciel.
The last one I looked at was Welsh, which has enfys. The etymology of this is trickier. The en- bit could be an "intensifier", a prefix that adds some kind of emphasis to the following element, and the fys part could be connected to finger or ring, so the origin might have been something like great ring.
