The entire municipality of Mahayag was once a sitio of Barangay Molave (currently Municipality of Molave), under the Municipality of Aurora. On May 9, 1960, by virtue of Executive Order No. 393 issued by President Carlos P. Garcia, Mahayag became an independent Municipality with the first appointed Municipal Mayor Hon. Saturnino Mendoza. Along with it, Barangay Delusom was also established as part of the 29 total barangays of Mahayag. Barangay Captain Andres Calderon became the first Punong Barangay of Delusom. Delusom is a woody area wherein the majority of its inhabitants are Subanos with 2 tribal leaders at that time: Ambolong Lomingo and Andoga Gandamon. The main agricultural products during that time were rice and corn where they cultivated the land utilizing the kaingin system. They used bolo and “urok” to plant the seeds and big stones and “lusong” to grind the corn and rice respectively. The term “Delusom” came from the Subanen term “Gelusong” which is defined as the action of grinding the rice.