Shamir's Secret Sharing, named after its creator, Adi Shamir, who introduced the concept in 1979, is a method for securely sharing a secret (like a private key) in a distributed manner.

The secret is divided into distinct parts, giving each participant its own unique part, with the requirement that a certain threshold must be combined to reconstruct the original secret. In the context of Bitcoin, Shamir's Secret Sharing can be used to enhance the security and flexibility of multisignature wallets and backups.

More information on Shamir's Secret Sharing can be found by reading the official Codex32 site and watching the visual explainer below.