Meaning

noun writes (books or stories or articles or the like) professionally (for pay)

noun someone who originates or causes or initiates something

verb be the author of

originFrom Middle English auctour, from Anglo-Norman autour, from Old French autor, from Latin auctor, from augeō (“to increase, originate”). The h, also found in Middle French autheur, is unetymological as there is no h in the original Latin spelling. The OED attributes the h to contamination by authentic. Doublet of auteur.

Etymology from Wiktionary, CC BY-SA 3.0