Siddhis (Sanskrit and Pali; Devanagari सिद्धि; Tibetan: དངོས་གྲུབ, THL: ngödrup , Chinese: 悉地, 成就) are spiritual, paranormal, supernatural, or otherwise magical powers, abilities, and attainments that are the products of spiritual advancement through sādhanās such as meditation and yoga. The term ṛddhi (Pali: iddhi, "psychic powers") is often used interchangeably in Buddhism.
Siddhi is a Sanskrit noun which can be translated as "perfection", "accomplishment", "attainment", or "success". In Tamil the word Siddhar/Chitthar refers to someone who has attained the Siddhic powers & knowledge. Chitta is pure consciousness/knowledge in Sanskrit also.
The earliest appearance in Indian history of the idea that magical powers are generated by spiritual practices is the account of the use of jhāna to gain iddhi appearing in the Pāli Canon in the Samaññaphala Sutta of the Digha Nikaya.
The Yoga Sutras of Patanjali, compiled around 400 BCE from many older traditions, goes into great depth about how to obtain various siddhis.