A four-letter synonym for Ireland is "Eire" - but this is not an abbreviation.
Norther Ireland
Church of Ireland (Anglican)
The abbreviation used on CARS when people travel aborad is IRL for example.
The word for Ireland in the Irish language is Éire.
IE is the correct abbreviation. People sometimes mistakenly say it's IRE or IRL.
The abbreviation at the end of Irish domain names is ie. Anyone applying for an ie domain name who does not reside in the 32 counties of Ireland must prove a Real and Substantive Connection with Ireland.
The usual abbreviation is M - as in MP for Member of Parliament, or MIAPI for Member of the Institute of Advertising Practitioners in Ireland, and many others.
NIAMH stands for the Northern Ireland Association for Mental Health.
N. I. - many people call it Ulster, but this is technically incorrect as a third of Ulster is in the Republic
Before 1924 Ireland was part of the team that was represented by GBR. Since 1924 Ireland has been represented by its own team (IRE). GBR is the abbreviation for Great Britain and Northern Ireland. Athletes from Northern Ireland can compete for GBR or IRE.
UK , for United Kingdom.