The story
From ER (“Einstein-Rosen bridge”) and EPR (“Einstein-Podolsky-Rosen paradox”). From Einstein (Albert Einstein), Podolsky (Boris Podolsky), Rosen (Nathan Rosen).
Etymology from Wiktionary, CC BY-SA 4.0.
ER=EPR
Today it means: A conjecture equating the effects of quantum entanglement (EPR) with a wormhole (ER) connection between the entangled particles, relating quantum physics to spacetime physics. Full definition →