The siren is from Greek mythology, where they lured sailors to their watery graves by appearing as beautiful maidens and singing an enchanting song.
The character Fredrick was mentioned before in The Shepherd (2011). When one of King Midas's knights went to remove Midas's gauntlet, the king said, "Remember what happened to Fredrick." In this episode "What happened to Fredrick" is revealed.
"Nostos" is Ancient Greek for "homecoming." It is the root of the word "nostalgia," meaning longing for the past, fitting for magical water that can return something that was once lost.
A segment with Ruby standing in the doorway outside Granny's Diner was deleted from the episode.
Ruby's car from The Price of Gold (2011) was supposed to appear in this episode, but it did not appear in the final version.