phony (adj.) Look up phony at
also phoney, "not genuine," 1899, perhaps an alteration of fawney "gilt brass ring used by swindlers."
His most successful swindle was selling "painted" or "phony" diamonds. He had a plan of taking cheap stones, and by "doctoring" them make them have a brilliant and high class appearance. His confederates would then take the diamonds to other pawnbrokers and dispose of them. ["The Jewelers Review," New York, April 5, 1899]
The noun meaning "phony person or thing" is attested from 1902.