Dira is a word which is used again and again in the Upanishads. It basically means the one qualified for Vedanta. The intelligent one gives up happiness and sorrow by developing concentration of mind on the self with capital S. Nachikita meditates on the old deity who's inscrutable, lodged inaccessibly,. located in the intellect and seated in the midst of misery.
Swami Sarvapriyananda teaches the Katha Upanishad, which is one of India's most revered texts and a part of the Vedas. It is a collection of philosophical poems representing a conversation between the sage Naciketas and Yama (god of death). They discuss the nature of Atman, Brahman and Moksha(liberation).