Chev was the native tongue of the Chev species.
The Chevs were a slave species to the Chevin, so the Chevs also spoke Chevin. As a result, Chev language was heavily influenced by Chevin language.
Chevins usually encouraged their Chevs to practice Basic, so that they become more useful and also a commodity that could be sold to other species. However, Basic influence on Chev language was only slight.