Spirit (of Glenans)
Well-known member
You're right, "Republic of Ireland " is purely a vernacular term.Not in any version of the constitution that I can find.
They all state "The name of the State is Éire, or, in the English language, Ireland. "
eg: Irish Statute Book
or Constitution of Ireland (consolidated text) - Wikisource, the free online library
Do you have a link to your version?
(not that it matters too much. I don't think the Germans get upset that we call their country Germany rather than Deutschland. There are political reasons why some people might prefer one name or another for Eire / Republic of Ireland. But it's probably best not to let this discussion descend into politics)