In Bengali, a bil is a stagnant water body formed out of river movement, usually a horse shoe lake.

In 1971, Ketnar Bil fell under the Gaurnadi police station of the then Sadar sub-division of the undivided Barisal district.

They set up bunkers at the bridges in Batajor, Bhurghata, Mahilara, Ashokkathi and Kasba in Gaurnadi police station area.

[2] On 14 May, locals under the leadership of one Chitta Ballabh, attacked an army patrol from the front with spears and shields killing four soldiers in Donarkandi.

[2] Enraged by this attack, the next day at around 10 am, a contingent of around 100 Pakistani soldiers, proceeded towards the west past Kasba and Chandshi.

[2] The Pakistani army then set hundreds of deserted houses on fire, killing cattle and other livestock.

In 2011, Deputy Command A. R. Sarniabat of Muktijoddha Sangsad visited Ketnar Bil and designated it as the largest mass killing site in southern Bangladesh.