Hindu word is derived from river sindu, which was difficult for Arabs to speak. So, they start using word Hindu. Later on people leaving near sindu are refer as hindu. European people also start using hindu for people those are other than Turks or Arabs. But they refer Sindu to Indu and later Indus.
Hindu word origin is not clear but people leaving in India are practice similar religion since 5000 years. Sometime they refer as Hindu or Ajivika.
As Hinduism is developed over a period of time without any messenger or prophet. Hinduism includes basic concepts for life like
1. You can be athiest .
2. Hinduism is dynamic and changed over the time
3. Allow women to choose partner by “Swayamvar”
4. Lot of Holy Books Ved, Gita(Bhagwad, manu etc ), purans , manusmriti