"'S e ur beatha a thidseir."
Translation:You are welcome teacher.
It's the "same difference" as in "tapadh leibh" and "tapadh leat" - English has lost all those nuances in the use of "you" (thou/thee), where many other languages have retained them. I think most have just the two forms, like French and Gaelic, with associated variants with prepositions etc, and occasionally three, like German - du - informal singular, ihr - informal plural, Sie - formal, either singular or plural
I'm told that it's to signify that our relationship with God is the most intimate and personal relationship we can have, that He is God our Father. Which kind of falls down when Gaelic services address God as thu, as I'd have expected, but Gaelic speakers address their actual fathers as sibh, which I would not have expected.
Interesting that the singular is winning in Scandinavia while the plural has essentially won in English. (And don't anybody ask about "euch" in German. I did once and regretted it. The answer started to go on about the Hundred Years War.)