Lagum was born to her single mother Sidonia Ayaa in Kampala. After losing her job, her mother relocated to Kitgum to move in with her grandparents. In her early years, Lagum was teased due to being much taller and thinner than her peers. As a child, she aspired to become a lawyer. Lagum moved back to Kampala to continue her schooling in St. Jude Primary School, Katikamu Seventh Day Adventist Senior Secondary School and St. Lawrence High School
