early 15c., ficcioun, "that which is invented or imagined in the mind," from Old French ficcion "dissimulation, ruse; invention, fabrication" (13c.) and directly from Latin fictionem (nominative fictio) "a fashioning or feigning," noun of action from past participle stem of fingere "to shape, form, devise, feign," originally "to knead, form out of clay," from PIE root *dheigh- "to form, build."
Meaning "prose works (not dramatic) of the imagination" is from 1590s, at first often including plays and poems. Narrower sense of "the part of literature comprising novels and short stories based on imagined scenes or characters" is by early 19c. The legal sense (fiction of law) is from 1580s. A writer of fiction could be a fictionist (1827). The related Latin words included the literal notion "worked by hand," as well as the figurative senses of "invented in the mind; artificial, not natural": Latin fictilis "made of clay, earthen;" fictor "molder, sculptor" (also borrowed 17c. in English), but also of Ulysses as "master of deceit;" fictum "a deception, falsehood; fiction."