During the 16th century , Bintulu was named " River de Burulu " by Portuguese cartographers . There are several legends surrounding the name Bintulu . During the Brooke dynasty , the indigenous Iban people practised headhunting to maintain their social status in the community . They threw the heads into the Kemena River , after which the heads had to be collected from the river . The practice of collecting the heads was known as " Mentu Ulau " ( picking heads ) in the local native language . Another story relates that two Iban warriors named Bernik and Jelab built houses along the river . They and their followers frequently carried out preservation of severed heads near a small river stream branching off from Sebezaw River because the river bank was flat and wide . Therefore , the small river stream was named " Mentu Ulau " river . Outsiders who came to Bintulu subsequently pronounced the name as " Mentulau " , and later the name evolved into " Bentulu " and , finally , " Bintulu " .