Jesus is life?

Even Gaelic has its urban myths. One of them is that 'S e do bheatha supposedly is Is E do bheatha, as in He (Jesus or God) is your life. Nice try but no.

It's true that if you dig a bit further back into history, you come across dia do bheatha in Old Irish (yes, fortunately they wrote things down, so we have an instance of CuChulainn greeting Fergus with Fuit! Día do bethu, a phopa Fergus. So while this looks bit like it might be invoking anthropomorphised omnipotent beings, there's an immediate problem. Yes, it's unlikely to be the Christian pantheon because the Fianna didn't do Christianity.

Bearing in mind very similar Old Irish formulae, such as

• rotbia-su fáilte "you will have welcome"
• rotbia in failti sunda againni "you will have welcome here at us"

it is much more plausible that the origin of this phrase was rotbia de bethu "you will have/may you have life". This would regularly turn into día do bheatha, then dé do bheatha, further reduced to sé do bheatha and the re-analysed ultimately as 's e do bheatha. This also explains neatly, by the way, why this seemingly is ungrammatical i.e. in reference to beatha, you would expect Is í do bheatha rather than Is é.