The Collaborative International Dictionary of English v.0.48:

Hindoo \Hin"doo\, Hindu \Hin"du\ (?; 277), n.; pl. Hindoosor
   Hindus. [Per. Hind[=u], fr. Hind, Hind[=u]st[=a]n, India.
   Cf. Indian.]
   A native inhabitant of Hindostan. As an ethnical term it is
   confined to the Dravidian and Aryan races; as a religious
   name it is restricted to followers of the Veda. Hindoo
   calendar