The story
The scam messages usually claim to originate from Nigeria, though this is often a spoof.
Etymology from Wiktionary, CC BY-SA 4.0.
Nigerian scam
Today it means: An attempt to defraud by sending out large numbers of emails, each stating that the recipient is entitled to receive a large amount of money, but will need to supply banking account details, or to send payment for fees, before the payment can be passed on. Full definition →