All symbolic communication is learned, negotiated, and dynamic. We know that the letters b-o-o-k refer to a bound object with multiple written pages. We also know that the letters t-r-u-c-k refer to a vehicle with a bed in the back for hauling things. But if we learned in school that the letters t-r-u-c-k referred to a bound object with written pages and b-o-o-k referred to a vehicle with a bed in the back, then that would make just as much sense, because the letters don’t actually refer to the object and the word itself only has the meaning that we assign to it.
I often think about this with different words. For example: a family friend had a friend who taught their very young child that yes was no and no was yes. It sounds funny, but I can only image the confusion that caused that poor kid as it grew and learned more advanced communication skills.