The story
From real (in real estate) and -or. Coined by Charles N. Chadbourn in 1916, on the model of Latin agent nouns ending in -tor (such as actor, creator), to refer to real-estate professionals who are members of the National Association of Realtors, a trade association in the United States. Equivalent to realt(y) + -or.
Etymology from Wiktionary, CC BY-SA 4.0.