Collar as used in BDSM
BDSM is a variety of erotic practices involving dominance and submission, role-playing, restraint, among other practices. The practices exist within the BDSM community and in the general population.
The term BDSM dates back to 1969; however, the origin of the term BDSM is unclear and is believed to have been formed either from joining the term B&D (bondage and discipline) with S&M (sadomasochism or sadism and masochism), or as a compound initialism from B&D, D&S (dominance and submission), and S&M. Regardless of its origin, BDSM is used as a catch-all phrase to include a wide range of activities and distinct subcultures. (Full article...)