There is no single word for the expression creative writing. This is because it arose in the post war period, largely in connection with with education and above all in relation to the teaching of English in schools in the anglophone world.
Historically, most writing in English lessons concentrated on exercises of dictation, comprehension, paraphrase and précis. Essays came later, either on ethical and historical topics or as interpretation or appreciation of some work of literature.
The idea that that children should express themselves by writing their own poems or stories, grew early in the twentieth and became increasingly established after 1945, reaching its zenith in the 1960s. But it was never given a name.
There is a general term for writing: LITERATURE and in days gone by writers were often described as men of letters (ignoring, of course, in those times, the existence of female writers).
But literature will not really do. It is true that the ‘English Literature’ taught to British schoolchildren would cover the content of what is generally understood by creative writing. But it does not involve students in creating anything.
No novelist, playwright or poet known to me has ever claimed the title of creative writer.
Creative writing is a well established term. Everyone knows what you mean if you tell them you are taking a creative writing course. It doesn’t take long to type. If you want to shorten it for. tweet, try CW. Acronyms are very popular.