Fictitiously

Names, characters, places, and incidents either are the product of the author's imagination or are used fictitiously.

Source: tatoeba (2060835)

Since the term 'imagination,' absolutely in a grammatical sense, means a certain, definite idea, that is, an affection of the mind, representative or implying a representation, in the same way I acknowledge that nothing physical, or even in any sense moral, could be conceived by the mind, or could be understood precisely, if not by means of a figurable example: and not only, as they say in the schools, concretely, but especially individually: for at the lowest degree, this can be done vaguely and even fictitiously by an arbitrary representation, which is nevertheless figuarable or imaginable.

Source: wiktionary