Dia dhaoibh!

I have a couple of questions about the words for 'rainbow' in Irish. Being a linguist, I love to learn not only what the words mean, but also how they work, their morphology and etymology. So when the dictionaries gave me the two variants mentioned in the subject, it piqued my interest.

I figured out that bogha báistí is essentially what it is in English: "a bow of rain".
Tuar ceatha turned out to be more difficult. I found that tuar means "sign, omen" and assumed that ceatha is a genitive case of some word, but I can't seem to guess the nominative form of it. So, "a sign" of what?

Also - is there any difference in usage of these two variants? Is "bogha báistí" a calque from English? Google returns just a few thousand hits for it, but more than 1.5 million for "tuar ceatha".

Sorry for so many questions about such a simple word, I love to dig deep when it comes to linguistics. Also sorry for any mistakes, English is not my native language and I'm just a beginner in Irish.

Dia is Muire duit a Pangur agus sé do bheatha go dtí an fóram! (Welcome to the forum)

Ceatha is the genitive of cith, meaning shower (of rain). Tuar ceatha or tuar-cheatha is what you would hear in the north, in Ulster - never bogha báistí. I've heard bogha ceatha in other places, however.

Slán,

Domhnall

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Ultach mé agus Gaeilg Uladh a labhraim go measardha maith!

There is also Tuadh Ceatha = Axe of a shower of rain.

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The dialect I use is Cork Irish.
Ar sgáth a chéile a mhairid na daoine, lag agus láidir, uasal is íseal

Dinneen (1904) has the following for "rainbow":



Dinneen (1927) also has:



Indicating that bogha báistighe (Inishm.) was local to Inishmaan. It could still be a calque but on the other hand what is a "rainbow" but "an arch caused by (refraction through) rain"?

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).

Go raibh maith agaibh! Tá sé seo an-shuimiúil.

Thanks to all of you, and especially to Breandán for mentioning Dinneen's dictionary. Can't believe I didn't know about this treasure.
This kind of digging really helps (me, at least) to understand the 'spirit' of the language better.

a gaeilgeoir pal from kerry says
, a nice amalgamation.