What does iKr stand for?
It stands for "iKr". The game originated in Sweden, and the Swedish national currency is the kronor, abbreviated Kr. Some players have insisted that iKr therefore means "imaginary Kronor" or "internet Kronor", but the game's originator never said there was a specific meaning.
More countries have been added since then, and their currencies all use a lower-case i followed by the currency symbol of the country — iEUR (euro) in Portugal and the Netherlands; iYTL (new lira) in Turkey; and i$ (dollar) in the United States.