There is a river in Tutong called Sungai Penabang. There is a place in Banjarmasin in Kalimantan, Indonesia where there is a group of people who spoke the Tutong language and the group claimed that their ancestors came from Pangkalan Jong, Tutong. What is the link between the two?
According to a Tutong legend, Pangkalan Jong in Kampong Keriam, Tutong is one of the earliest inhabited places in Tutong. It's strategically located where two rivers meet Sungai Kelakas and Sungai Birau. Because of its wide bay, ships used to berth there and that's why it is called Pangkalan Jong (Jong meaning ship and pangkalan meaning port).
At one time, there was a proliferation of a species of fish called Ikan Karok. These fishes grew to such large proportion and in such large numbers that they fill in all the waters in the rivers and in the water wells to the point that villagers in the area could not get fresh water. Many villagers emigrated away from the village until one night an elderly man had a dream that he should beat the water with a rope made out of tuba roots. The villagers followed the advice and many fish died to the point that the river was choked (terbabang). That's why the river was called Sungai Penabang.
One group that left the village ended up in Banjarmasin. That's why up to now you can still find some Tutong speakers in Banjarmasin, Indonesia.