I'm not a tax expert however I believe it works like this:
if you like me are a foreign national, Swedish in your case, that moves to Ireland with the intention of staying only 4 years and then return to Sweden (and retain assets and connections in Sweden), you will be considered non domiciled in Ireland for tax purposes. Ireland only taxes you on foreign income if it's remitted to Ireland. This is however valid for income generated by some specific asset classes and not others. The remittance basis doesn't apply for example to gains generated by ETFs, Offshore funds, deposit accounts, money markets, profits made by forex/currency exchange operations, but it applies to gain made on shares for example (as long as the company issuing the shares is not tax registered in Ireland) or it applies to gain made with rents. Your ISK appears to be a deposit account ? so if this is the case then I believe you are taxable in Ireland on the gains made. The first €1,270 of taxable gains in a tax year are exempt from CGT, above that you will have to pay the 33% minus the 0.88% that you already pay in Sweden. I don't know what's a ISK fund but had a quick look and looks like what's considered in Ireland to be a offshore fund. (which is taxed in Ireland at 41%)
This forum hosts a lot of high caliber tax experts that may give you better insights, otherwise maybe it would be a good idea to get some independent tax advise.
Franc