Saryanavat is the name of a lake mentioned in Vedic literature and may be the origin of the name of Haryana State in India. The name is found in several passages of Rig Veda. It is believed that the lake was filled with thickets of soma plant. Soma was an important drink offered to Gods in the Vedic age.
The name ‘Saryanavat seems to be derived from ‘sara’ meaning ‘munja, sarkanda or saccarum sara’ (somasyeva maunjavatasya – Rig Veda 10/34/1). Munjavan is one of the twenty four varieties of soma plant mentioned in the Vedas.
Saryanavat is translated by Rudolf von Roth, German Indologist, founder of the Vedic philology, as ‘covered with a thicket of reeds.’
The lake is called Saryana in the Jaiminiya Brahmana. The location of the lake as per this Brahmana is the lower western part of modern day Kurukshetra.
As per Mahabharata, there was a tirtha by the name of Sasayana on the bank of Saraswati. It was a pond in the shape of a rabbit. Taking a holy dip in the river cures various ailments, makes a person shine like the moon and it also acquired the merits of gifting a thousand cows. The holy pond is located a couple of stages above Vinasana. It is believed that Saraswati River disappeared at Vinasana.
Some scholars think that this odd and unlikely name, Sasayana, may have been a scribal error for Saryana, which is mentioned in Ganapthat of Panini’s Ashtadhyayi.
Research suggests that the word ‘Haryana’ may have been a corrupt form of Saryana representing a change of Sa to Ha, which is a common feature particularly noticed in some early dialects of northwest
Source – Notes taken from Encyclopedia of Hinduism Volume IX (IHRF). (page 300)