In both science and common sense, words are used to refer to specific things in the world. The word ‘hydrogen’ is used to refer to a gas that’s believed to make up three quarters of the matter in the universe. And the word ‘dog’ is used to refer to the hairy creatures that often wag their tails when people say ‘walk’.
The words, or the ideas behind whole patterns of thought, get their sense from being about certain things, and it doesn’t make much difference to the aboutness if the objects they’re about are real or fictional. An idea can refer to the current president of the USA, to Christopher Columbus, or to the Pied Piper of Hamelin with equal ‘aboutness’.
All that matters is that the idea points towards a form of life, and even fictional characters are forms of life, with patterns of existence that statements can be wrong or right about.
It is even possible for an idea to have aboutness when the object it refers to does not exist, as in ‘the present day king of France is bald’. France doesn’t have kings any more, but as soon as you mention one, one appears, picked out from the infinite pool of the possible by the light of the imagination.