SM (Japanese usage)
In Japanese, SM (read esu-emu) is the everyday umbrella word for sadomasochistic play and culture, a field in which kinbaku has long been placed.
SM abbreviates sadomasochism, combining S for sadism and M for masochism, and is read esu-emu (Japanese Wikipedia; Jisho). Japanese uses it as an umbrella term for the whole field, from soft play to hard practices, and places rope bondage inside it, with kinbakushi as its rope specialists. The letters also label roles, as in M-jō, a masochistic woman (Shibari Study). According to Ugo of SMpedia, speaking to Kinbaku Today, the word became widespread around 1970, after Kitan Club had nurtured the scene. Japanese Wikipedia connects the growth of kinbaku to postwar SM magazines such as SM Magazine, launched in 1968, and lists SM clubs and SM bars as venues.