Is this the right question? What are the assumptions or affirmations that make this question possible? First, that there is some sort of relationship between words and things.
And what is it to say that there is such a relationship? It is, first and foremost, to say that there are two distinct phenomena, words and things, and that they relate in a certain way, and that the way in which they relate is through reference. Words are on the one side and things on the other, and lines are drawn to connect the two sides, so that the thing is evoked by the word, and the word evokes the thing. No humans are required in this picture. The relationship is between words and things.
In practicing philosophy, it is good to ask what the aesthetic impression is that we get from a certain question. What are the images that such question brings about? For those images will attract and justify certain kinds of answers. Answers aren't facts; they are particular responses to particular questions. An answer is made possible by its question, which was made possible by a premonition of the answer. A question becomes possible only when we are already hinting at the answer, or at least have a field of possible answers.
When we ask “how does a word refer to a thing?,” the scene that comes to mind is: the word is there, perhaps in the realm of thought or in the world of ideas, or maybe in our minds, and at some point it comes to refer to a thing, which, since the beginning of time, has had all of its properties, and has just been waiting for the birth of man to be baptized. If we reformulate to “how do things come to be referred to by words?,” now it is the things that are there, in the material world, and the words that show up to refer to them.
Perhaps, we might conclude, what is missing from this question is the human that uses words to refer to things. Words alone don’t just refer; someone is using them for that purpose. And so we might want to reformulate “How does a human use a word to refer to a thing?” And then we have humans taking the word from the one side and the thing from the other and making a link between them.
Here, still, words and things are distinct realities that are linked to one another. Reference seems to require this distinction between what refers and what is refered to and seems to demand some sort of temporal ordering of these parts: what comes first, what is referred to or what refers? Or perhaps it requires just the opposite: that both sides are brought about simultaneously. For what is referred to cannot exist without what refers, and what refers cannot exist without what it refers to.
So we might want to imagine that reference is not a permanent eternal connection between two pre-existent sides, but rather some sort of spark that exists only in a certain context and only during the time it is made use of, and then disappears and never reappears in quite the same way.