What is fictional narrativization of history ?

A great question.

To narrativize something means to tell a story about it. (A narrative is a story.) A fictional narrativization would be a story that is fictional. A fictional narrativization of history would be a fictional story about history.

The most common form of this would be what's known as historical fiction, in which authors take the facts of history as the base or framework for their story. They then present a fictional story within that frame. These stories might focus on famous historical figures, bringing the inner life of these figures to life, like Robert Graves did in I, Claudius. Other authors invent their characters, so they can provide an observer's perspective on famous people or events, like Gary Blackwood did in The Shakespeare Stealer, which invents an orphan who tries to steal copy of Hamlet (for complicated reasons).

There are more complicated forms of fictional narrativizations of history. Some are what are known as "alternative history," which rewrites the actual facts of history, asking what would have happened if things were different.