The Pali Abhidhamma already names issa, envy, among the secondary mental factors that can accompany an unwholesome state of mind, distinct from the three root kleshas but built on top of them, and it defines the factor narrowly: not simple desire for what another has, which is closer to raga, but specific displeasure at another's good fortune, a resentment of their possessing it rather than a wish to possess it oneself.
When later Vajrayana literature organises the poisons into a set of five to match the five Buddha families, irshya takes the fifth place, completing a scheme that began with the three roots and widened to admit mana and irshya as the two poisons most associated with how a person positions themselves relative to others rather than with an object desired or resisted directly.
The Princeton Dictionary of Buddhism notes that this five poison arrangement is a systematisation found chiefly in Tibetan scholastic and tantric sources rather than in the earlier Pali material, which keeps its analysis closer to the three roots and treats issa as a subsidiary factor rather than a poison of equal rank. Both framings agree on the basic phenomenon, resentment of another's success experienced as a fire in one's own mind, and both treat it as corrosive to the practitioner rather than to its object, a point repeated across commentarial literature on the mental factors.