लंगोट, laṅgoṭ 

The loincloth of a yogin or ascetic (kaupina). It is associated with the observance of brahmacharya, the control of the senses and instincts.

The langot is not just a piece of clothing, it is a particular kind of energy, Shakti, that sadhaka places on the genital area to sublimate sexual energy and raise it upwards along the sushumna. In the Nath Tradition, Langot Guru teaches the use of the langot, and explains how to transform sexual energy into spiritual energy. This initiation is called langot diksha. With this diksha, a special mantra is transmitted that must be recited on the langot, which will actually help in controlling one's power (virya).