https://www.youtube.com/watch?v=H4dGpz6cnHo is the "original"[1] video, though many SCP games had similar environments and settings beforehand. See various memes spawned from it, such as https://www.reddit.com/r/tf2/comments/tb0v29/the_backrooms/ and https://www.youtube.com/watch?v=72Y0LHM1vGs

[1] Responsible for the most recent set of trends, but derivative of creepypasta that's been gathering traction for a while. https://knowyourmeme.com/memes/the-backrooms - points to 2018, but I'm pretty sure that SCP wiki had versions before then.