Why do people name dogs based on how they look?

When humans hear the names Lassie, Rover and Fido, they immediately know that refer to dogs. For dog's themselves, their name is, perhaps, the single most important word that they will ever learn. Think of it this way, a dog lives in a sea of human sounds and, with only the language ability of a human 2-year old, it has to decide which words are directed at it and which are not. Thus if you say to another family member "Why don't you come here and sit down beside me," how does the dog know whether the words "come", "sit" and "down" were meant as commands for him? Obviously, if you were looking directly into the dog's eyes and had his full attention the "sit" or "down" would clearly be directed at him and he should know that you mean for him to respond. In the absence of that sort of body language, however, the dog's name becomes the key to his understanding. In effect, a dog's name becomes a signal which tells him that the next sounds that come out of his master's mouth are supposed to have some impact on the his life. Thus a dog's name linguistically translates into something like "This next message is for you."