If you read the chapter of St. Augustine, you can note that the author establishes a kind of equation :
tria : salus = Chananaei : *Chanani. The word connector for this equation is unde « from which, whence ».
In my opinion, Augustine also gives us the solution, the key to read this equation : the corruption of a single letter (corrupta scilicet sicut in talibus solet una littera). We must be sure of the lesson transmitted *Chanani (which are the other lectiones in the manuscript tradition?) to exclude that the corruptio concerns a consonant (KNN). Alternatively, as the text is delivered, the question seems to concern the final-vowel sequence - aei (it is the only element changing fromChanani to Chananaei), which certainly may have been facilitated by the phoneticism Phoenician-Punic that provides a suffix yod for the ethnics.
Kind regards,
Maria Bianco