Many airports have "local" acronymns for the name of their airport, which differ from the official airport code used for booking travel.
Orlando International Airport, local: OIA, official: MCO
Kansas City International, local: KCI, official: MCI
Louisville International, local: LIA, official: SDF
Many of the current commercial airports were originally military bases, so the official name came from the name of that base. OIA was established at McCoy Air Force base, thus the official name "MCO" for Orlando International. Louisville was established at Standiford Field, thus "SDF" for Louisville International.