What's an ECU? Oh yeah, European Currency Unit! Remember that precursor to the Euro? To be honest, I remember thinking "what was wrong with the ECU?" when the doomed Euro was introduced. Side note: monetary policy must be aligned with fiscal policy.
https://en.wikipedia.org/wiki/European_Currency_Unit
Anyway, the ECU. Sounds like Libra employs a "basket" of fiat currencies a la the ECU. That aspect may be the only good thing about Facebook's attempt at a stablecoin, Libra. As much as I like a basket feature, I have a nasty feeling Libra may turn out to be another huge power grab, similar to 100 years ago when most governments except for the USG went off the gold standard and the USD became the world's reserve currency. That scheme turned out to be an invitation to debasing currency and the foundation of modern warfare.