The Spanish Prisoner is a confidence trick originating in the late 16th century. In its original form, the confidence trickster tells his victim (the mark) that he is (or is in correspondence with) a wealthy person of high estate who has been imprisoned in Spain under a false identity. Some versions had the imprisoned person being an unknown or remote relative of the mark. Supposedly the prisoner cannot reveal his identity without serious repercussions, and is relying on a friend (the confidence trickster) to raise money to secure his release. A classical Pigeon Drop game archetype, the confidence trickster offers to let the mark put up some of the funds, with a promise of a greater monetary reward upon release of the prisoner plus a non-pecuniary incentive, gaining the hand of a beautiful woman represented to be the prisoner's daughter. After the mark has turned over the funds, he is informed further difficulties have arisen, and more money is needed. With such explanations, the trickster continues to press for more money until the victim is cleaned out, or declines to put up more funds.
Spanish Prisoner Wikipedia
Key features of the Spanish Prisoner trick are the emphasis on secrecy and the trust the confidence trickster apparently places in the mark not to reveal the prisoner's identity or situation. The confidence trickster will typically claim to have chosen the mark carefully, based on his reputation for honesty and straight dealing, and may appear to structure the deal so that the confidence trickster's ultimate share of the reward will be distributed voluntarily by the mark.
Modern variants of the Spanish Prisoner include the advance-fee scam, in particular the Nigerian money transfer (or 419) scam. In the advance-fee fraud, a valuable item must be ransomed from a warehouse, crooked customs agent, or lost-baggage facility before the authorities or thieves recognize its value. In the Nigerian variation, a self-proclaimed relative of a deposed African dictator offers to transfer millions of ill-gotten dollars into the bank account of the victim in return for small initial payments to cover bribes and other expenses. More recent examples feature people sharing the same surname as the intended victim, with the scammer guessing the surname from observing patterns in e-mail addresses, or obtaining full names from harvested email headers. Another variation spreads via hijacked Facebook accounts, where a message is sent to all the Facebook-friends of the victim, claiming that the victim is in a foreign country, has been robbed, and needs one of the Facebook-friends to "send money" via Western Union to pay hotel and travel bills.