From Hindupedia, the Hindu Encyclopedia
By M. A. Alwar
Irāvatī is a feminine form.
It is derived from "irā vidyate'syāḥ iti" which means 'She who possesses liquor/water (irā)'.
It can be split as irā+matup.
In Mahābhārat, it was used to refer to
“Vipāśā, śatadruḥ, candrabhāgā, Sarasvatī, Irāvatī, Vitastā, Sindhuḥ, and the divine river Gaṅgā”
- Shabdakalpadrumah by Raja Radhakantdev, Varadaprasada Vasu, Haricarana Vasu