One of god Viṣṇu’s (Vishnu’s) one thousand names. To explain the meaning of the name Anādi (Anadi), the annotator Saṃkarācārya (Sankaracharya) has said—

ādiḥ kāraṇamasya na vidyata iti
                                       anādiḥ sarvakāraṇatvāt.

God himself has created the world, hence he can be called the earliest kāraṇa (karana, or reason) behind the creation of the universe. But it is impossible to deduce how or for what reason god himself was created. Just like he is endless and indestructible, he is also without origin. Therefore, Viṣṇu is renowned as Anādi.