The title comes from the original English translation of Dante's Divine Comedy, specifically the inscription over the gates of Hell - "Abandon All Hope, Ye Who Enter Here."
The side of the building used during Raina's attempt to escape Skye is actually the building used in Who Framed Roger Rabbit (1988). Although the inside of the building was not filmed, the front of the building facade was used as Eddie Valiant's office. The address is 1130 S. Hope Street, Los Angeles, CA 90015.
"...Ye Who Enter Here" originally aired on ABC on December 2, 2014, and according to Nielsen Media Research, was watched by 5.36 million viewers.