Back-formation from 煉銅術士/炼铜术士(liàntóng shùshì, “paedophile”), altered from 鍊金術士/炼金术士(liànjīnshù shì). Originally referring to the Bilibili streamer Goshiki Agiri Da Huyou (吴织亚切大忽悠), who was alleged to have openly expressed paedophilic ideas on the Internet.