Like when I would hear someone call a straw a "popote" I would think of my dad and him being from Mexico and I would say that that person was from Mexico and every single time I was right. Or when I hear someone call a straw "una pajia" I would then think of my mom and assume that they were from Guatemala and I would also be right. I used literacy to determine where people were from based on specific words they used.
With English it was a lot simpler, there aren't 3 to 5 different ways to say you. Although with English there were different meanings for different words. There would be a formal traditional meaning and a sort of urban slang meaning. For example "dog", growing up I would hear that word being used in different ways, to me it was a name for describing a four legged canine animal, a close friend, or how people described a man who will do anything to get into a girls pants. Not all people have the same meaning as I do, to them it might mean something else. Depending on where you're from or how you are raised it could mean something different. Also the different dialects in more of the way people pronounce their words. Like with the word "caramel" some people may pronounce it "car-ml" while others may pronounce it "car-a-mel" with one having an extra syllable I guess. Is this literacy? I guess you could say yes. You can tell whether or not a person is from the south or the north just by knowing the different dialects. People can be categorized by where they come from or by the way they pronounce or use their words.
With my siblings we had our own form of literacy when we would talk to each other or call each other. I have two sisters, one older and one younger, and a little brother. My older sister is named Norma and she is 20 years old now and when we were growing up my sister looked more Native American than she did Latino.