The tyet is an ancient Egyptian symbol of the goddess Isis; its exact origin is unknown. In many respects the tyet resembles an ankh, except that its arms curve down. Its meaning is also reminiscent of the ankh, as it is often translated to mean “welfare” or “life.” It seems to be called "the Knot of Isis" because it resembles a knot used to secure the garments that the Egyptian gods wore. The meaning of "the Blood of Isis" is more obscure, but it was often used as a funerary amulet made of a red stone or of glass. It is also speculated that the Tyet represents the menstrual blood flow from Isis' womb and its magical properties.
It is mentioned in the 156th spell for the Book of the Dead:
In all these cases it seems to represent the ideas of resurrection and eternal life.
Also called Tyet, Tet, the Knot of Isis, Buckle of Isis, Girdle of Isis, and the Blood of Isis.