The chit mahals were created out of territorial divisions dating back to the 17th century.
First, as the Mughal dynasty conquered much of india, several landed estates in East India remained under the control of the princely state of Cooch Behar. Similarly, some landowners in Cooch Behar allied themselves with Mughal India.
This odd situation persisted when Cooch Behar remained independent through the British Raj. When the subcontinent was partitioned in 1947, Cooch Behar chose to join India, but the new border did nothing to resolve the dilemma of the enclaves.
This process has even resulted in the world's only counter-counter-enclave: a two-acre plot of India embedded within a patch of Bangladesh, which exists within a patch of India, which in turn sits on Bangladeshi soil.
In 1971, East Pakistan won its independence and renamed itself Bangladesh. A land boundary agreement in 1974 proposed a resolution, but its measures remained unimplemented, and the status of the enclaves and their residents continued to be in diplomatic limbo.