The conjecture was proposed by Leonard Susskind and Juan Maldacena in 2013.[3] They proposed that a non-traversable wormhole (Einstein–Rosen bridge or ER bridge) is equivalent to a pair of maximally entangled black holes. EPR refers to quantum entanglement (EPR paradox).

The symbol is derived from the first letters of the surnames of authors who wrote the first paper on wormholes (Albert Einstein and Nathan Rosen)[4] and the first paper on entanglement (Einstein, Boris Podolsky and Rosen).[5] The two papers were published in 1935, but the authors did not claim any connection between the concepts.[2]

Quote:

*Susskind and Maldacena envisioned gathering up all the Hawking particles and smushing them together until they collapse into a black hole. That black hole would be entangled, and thus connected via wormhole, with the original black hole. That trick transformed a confusing mess of Hawking particles—paradoxically entangled with both a black hole and each other—into two black holes connected by a wormhole. Entanglement overload is averted, and the firewall problem goes away.*

— Andrew Grant, "Entanglement: Gravity's long-distance connection", Science News [8]

Preliminary evidence, though indirect, for ER = EPR is that a certain entangled pair has been realized as an ER bridge using AdS/CFT correspondence.[6]