Dia dhuit; a learner of irish who has some knowledge of it under his belt; but is trying to use a phrase a bit beyond the vocabulary he currently knows. anyway, some idiot responded to a remark I made on another website about the importance of saving the Irish language; claiming it should be allowed to die; while the main point of my reply that I am drafting is in english; I am using a couple isolated words of irish in it just to annoy him; turns out insulting people in languages they probably don't speak is fun. but one of them I need a second pair of eyes to look over. I need a translation of an English phrase before I can properly post the reply; I am intending to call the moron a "foreigner at heart"; I know just enough of the vocabulary of Irish to put a literal translation together by myself "a eachtrannach ag croí" (glossable as "foreigner-VOC at Heart-Dat"); but I would like someone to grammer and idiom check it; are the nouns correctly declined? does the idiom sound like something a person from the gaeltacht would say; or a literal translation from english? if the later; what is the cloest native structure? also should i use a gramatical varient of the noun in the phrase "Gallaibh" (of "fé ghlas ag Gallaibh" fame) or one of eachtrannach? normally i would not check every phrase i use especially with someone who favors the end of the language; but i feal that i should make a point to use correct irish in a statement all about the importance of irish. using the language more generally i would not go to such extreme ends. thanks in advance help please with that.

Your translation is too literal. The following would be correct, i think.

'Is eachtrannach thú i do chroí istigh' (You're a foreigner at heart.)

thanks; i suspected as much; my knowledge of irish is not good enough to know for sure; yet and i want to use correct irish when talking about the importance of irish.

also how do i simply render "foreigner at heart" in irish for the purposes of describing those who are against the restoration of the languages in other sentences?

If you want to switch to the third person (masculine), you would say 'Is eachtrannach é ina chroí istigh' (Literally: 'He is a foreigner in his heart inside.')

If addressing someone, you'd say: 'A eachtrannaigh i do chroí istigh'.

However, I think you are asking how to generalise it so as to make it independent of grammatical person. I'm not sure how you would do that. Maybe others could help. I think 'eachtrannach sa chroí istigh' (literally: 'a foreigner in the heart inside') might be reasonably acceptable for your purpose.

thanks for the help so far; to be able to use a language productively one must at the very least be able to put together different gramatical variations of the same word or phrase; nothing but fixed phrases is possible without that

also what is the plural form of the same phrase? i think i will use this phrase to insult anyone who thinks irish should be allowed to die;