who knows what lies at the heart of these words?
the shadow (also known as joe friday) [a fictitious and fictional construct bearing some fictive gravitas] do...

Fiction

[14c: from Latin fictio/fictionis a shaping, from fingere/fictum to fashion]. A general term for something created by the human mind. It has three aspects, each with an appropriate adjective: (1) (Both countable and uncountable). Not fact, but an invention of some kind, sometimes a fabrication or lie. The detective Sherlock Holmes was an invention of the writer Arthur Conan Doyle, and as such is fictitious; no such person ever lived. (2) (Usually uncountable). Not fact, but still part of reality; imaginative narrative, often part of literature: works of fiction in contrast with non-fiction, especially in bookshops and libraries. Here the fictional Sherlock Holmes is a fact in the sense that a character with this name appears in certain stories and films, and can be discussed in much the same way as a historical person. (3) (Usually countable). A special kind of 'fact': a social and cultural construct, such as a legal fiction that helps in the administration of the law, temporal fictions such as the days of the week, and geographical fictions like the Equator. Such constructs are part of life; they are fictive or constructed, and include products of imaginative storytelling. Fictively, Sherlock Holmes and the Equator are on a par, the one influencing crime writers, criminologists, and enthusiasts for the detective story, the other affecting geographers and sailors. The fictive generally subsumes both the fictional and the fictitious. Fictitious reports and fictional plots and characters are constantly being created in a language like English. At a certain level of discussion the language is itself fictive: something created by the human mind within a cultural system so as to serve certain social ends.

The Oxford Companion to the English Language, © Tom McArthur 1992