Nobody actually knows.
The leading story: a soldier named Orlando Reeves died in the Second Seminole War and the town was named for him. Except historians later found no record of any Orlando Reeves, only an Orlando Rees who carved his name into a tree and vanished. The backup theory: Orlando from Shakespeare's As You Like It.
Local note: a city named after either a war hero who may not have existed or a Shakespeare character. the answer is still anybody’s guess. But now you've got both theories.