The safety knot is a loop that closes on itself, tied by hand, and it appears on bracelets, anklets and clothing across China. The name is about the knot, not about anything it does: it is a well-known shape with a well-known name.
Braided polyester rather than silk, so it holds up to daily wear and water. The closure slides and the knot can be retied by hand if it works loose. Cold water wash; the weave tightens slightly as it wears.