One who originates
inventor, originator, creator, architect, framer, artificer, discoverer, innovator, maker, planner, strategist,
designer, projector, founder, father, organizer, prompter, producer,
fabricator, artist, composer, begetter, prime mover, initiator,
the brains*.
One who writes
writer, novelist, essayist, poet, short-story writer, dramatist, playwright, biographer, journalist, columnist, contributor, littérateur (French), belletrist, script writer, scenario writer, scenarist, screenwriter, librettist, scribe, penman, poetess, authoress, literary man, ghostwriter, encyclopedist,
lexicographer, scholar, critic, annotator, hack, hack writer, scribbler, freelance writer, ghost*; see also writer.
Antonyms reader*, audience, publisher.