P. Valsala wrote the novel after a rejuvenating experience in
Wayanad. It was published in 1972 by Sahithya Pravarthaka Cooperative Society. It went on to become a best-seller and won the Kumkumam Award for Best Novel in 1973. Kariat approached Valsala for permission to adapt the novel, and when she agreed, he asked
K. G. George,
S. L. Puram Sadanandan and Valsala to write separate scripts based on the novel. Noted South Indian actress
Sharada was originally chosen for the role of Mara. She turned down the offer when Kariat insisted that she dress like the tribal women of Wayanad. Later, Kariat fixed Jayabharathi, another leading actress of the time, for that role.
Nellu marked the debut of actor Mohan Sharma who went on to act in about 100 films in Malayalam. The film's production occurred at various villages near
Thirunelli in
Wayanad. It was produced by N. P. Ali under the banner of Jammu Films International. == Soundtrack ==