The story
From the common 19th-century practice of organ grinders training monkeys to dance to music played on a barrel organ in order to perform on the street and solicit donations.
Etymology from Wiktionary, CC BY-SA 4.0.
the organ grinder, not the monkey
the or·gan grind·er, not the monk·eyToday it means: Synonym of organ grinder (“the person who is in charge, rather than a lackey or representative; the person truly responsible for another's actions”). Full definition →