The first known eurodollar account was opened in France for China during the Korean War, in 1949 [1]. The phenomenon is a result of the Marshall Plan, which left lots of physical dollars overseas and thus outside U.S. jurisdiction.
My gut feeling is, that the EU, without any commodities, has a single choice: kick the Russian gas habit immediately, and force Russia to kill their western gas fields. Then pray they collapse in the next few years.
If the EU keeps paying - Russia's new Gazprom central bank controlled RuskiEuro reserves will stabilize its economy and it will rise like a phoenix from the ashes. Even if we kick the gas habit, this might still happen if Putin keeps his thumb on public sentiment enough.
[0]https://www.credit-suisse.com/about-us-news/en/articles/news...
It's not as if this hasn't happened before. The 'EuroDollar' came about after the invasion of Hungary in 1956. Russia has just invented the 'RuskiEuro', which is how the Bank of Russia will hold Euros for the duration - probably in settlement accounts at the National Clearing Centre in Moscow.
[0]: https://www.luxtimes.lu/en/business-finance/rubles-for-gas-p...