For my own reference, as much as anything else. I’m only listing things I’ve heard people say frequently that might not be obvious to a non-national:
Baltic: cold. Note to people from the north of England: this does not mean cold.
Blow-in: someone from outside the area. People often refer to themselves in a self-deprecating manner as a blow-in even though they’ve lived in a place for 30 years or more. I think it’s mainly used to illustrate that you’ll never be fully accepted as a local somewhere, but in a nice, slightly arch, kind of way to say it doesn’t really matter. Compare with: the Welsh burning-out English-owned holiday homes.
C’mere: excuse me, listen, that sort of thing. Not “come here”.
Feck: three common uses… expletive, verb to throw, verb to steal. Not sure if can be combined into something like “Feck! He’s fecked my phone and fecked it over the fence” – it sounds slightly contrived.
Gas: hilarious. “It was gas”, “he’s gas”, etc.
Grand: great / good / whatever. “It’ll be grand” is the verbal equivalent of a pat on the head and being told not to worry. Even though you should.
Hot press: airing cupboard. Press on its own can be just a cupboard.
Lads: refers to a group of people, whatever the gender make-up of it.
Long finger, on the: delaying something. Q: “Shall we drill a hole to ventilate the cloakroom and prevent extreme damp?” A: “No, that’s a messy job – best put it on the long finger”.
NCT: Irish equivalent of the British MOT test for vehicles. Presumably this ensures that for at least a very brief period people have cars with both headlights working.
PRSI: Social security. The British equivalent would be National Insurance, and in Ireland a person is identified by a PPS number in this system.
Stocious: very drunk.
Strand: beach. Same as German language and a bunch of others (see: https://en.wiktionary.org/wiki/strand#Etymology_1)
Streelish: untidy / unkempt.
Sure: appears at the start of some sentences to lend an air of confidence in the veracity of what follows. Not to be trusted.
Ye: you (plural). A useful distinction in the language that would otherwise need the vastly more complicated “you all”.
Yer man / yer one: Not actually anything to do with you, despite the possessive hint at the start. Used to refer to someone else in a non-specific way. Massively confusing at first.