The name of India is a corruption of the word Sindhu. Neighbouring Arabs, Iranians uttered's' as 'h' and called this land Hindu. Greeks pronounced this name as Indus.
Sindhu is the name of the Indus River, mentioned in the Rig-Veda, one of the oldest extant Indo-European texts, composed in the northwestern region of the Indian subcontinent roughly between 1700-1100 BC. There are strong linguistic and cultural similarities with the Iranian Avesta, often associated with the early culture of 2200-1600 BC.
The English term is from Greek Ἰνδία (Indía), via Latin India. Iindía in Byzantine ethnography denotes the region beyond the Indus (Ἰνδός) River, since Herodotus alluded to "Indian land". Ἰνδός, Indos, "an Indian", from Avestan Hinduš refers to Sindh and is listed as a conquered territory by Persian emperor Darius I (550-486 BC) in the Persepolis terrace inscription.