There's a condition (I forget what it's called) where people's senses get mixed up; they 'taste' sounds or 'hear' colours etc. Certain things get associated with certain other things - sounds get associated with certain things that correspond to the other senses.
There's evidence to suggest that we all have this condition, just most of us have it only to a small degree.
Take for example two shapes; one of these is rounded like a cloud, and the other one is spiky. I tell you that one of them is called a Kiki, and the other is a Boobah; you have to tell me which is which.
This becomes much more obvious when you can see the shapes, but about 99% of people would say the rounded shape is the 'boobah' while the spiked shape is the 'kiki'. It seems language is built right into us as a species.
I can see how this could be interpreted different ways, though. For example; it's possible that this developed in our species, and it allowed us to develop simple language which developed into complex language from there. It's also possible that there is a God who created us with language; and wrote the language directly into our genetic makeup.