[tragomaskhalos]

There is the theory that areas of our brain that were used for language acquisition as young children are "repurposed" as we age. From an evolutionary perspective, it is advantageous to commit a lot of brainpower to acquiring language initially, but thereafter this is not a particularly critical skill (esp. in traditional small monolingual communities). So I'd suggest that in your case this process has just been carried out to an extreme degree.