Andor's Prison Floors Are Straight Out Of The Expanded Universe
Although the incredibly broad "Star Wars" Expanded Universe was declared non-canon back in 2014 (renamed "Star Wars: Legends" thereafter), we've since seen a variety of assets from that Expanded Universe incorporated into numerous "Star Wars" films and television series.
Perhaps the most obvious example of this is the Expanded Universe character of Grand Admiral Thrawn, who became a major villain in the animated series "Star Wars: Rebels," where he was voiced by Lars Mikkelsen. Thrawn was also referenced by Ashoka Tano (Rosario Dawson) in Season 2 of "The Mandalorian," and will likely play a major role in the upcoming Disney+ series "Ashoka."
This trend of adapting assets from the Legends continuity has continued into the recently-released Disney+ series "Andor," which references several planets from the Expanded Universe, including Fest, Mimban, and Fondor (via Collider). In fact, Episode 8 of "Andor" actually features a pretty significant easter egg which is ripped straight out of the Expanded Universe itself.
Tunqstoid Steel was a metal first introduced in the Expanded Universe
In Episode 8 of "Andor," the titular thief and rebel spy Cassian Andor (Diego Luna) finds himself imprisoned in an Imperial Labor Camp on the planet of Narkina 5, where the floors are made from Tunqstoid Steel — an extremely conductive metal which shocks the prisoners into submission whenever they are being disobedient.
Fans of the "Star Wars" Extended Universe will know that Tunqstoid Steel comes from the 2009 novel "Fate of the Jedi: Abyss," written by Tony Denning; where it is described as an absurdly heavy material used for making blast doors (via Wookieepedia). Indeed, the novel describes how the extreme weight of Tunqstoid makes it so that powerful magnets are needed to pull the doors apart and that blast doors made from Tunqstoid can even stop a Jedi from passing through.
That said, the original source material doesn't actually make any references to the conductivity of this material, nor is it described as being used for floors. Although the name "Tunqstoid Steel" is, in fact, pulled directly from the "Star Wars" Expanded Universe, the material we see in "Andor" certainly functions much differently than its literary counterpart — though it's still interesting to see how the Expanded Universe continues to impact actual "Star Wars" canon all these years later.