SegWit
Concept
Segregated Witness, an upgrade activated in 2017 to store transaction data more efficiently, allowing more data per block.
Mentioned in 3 videos
Videos Mentioning SegWit

Nic Carter: Bitcoin Core Values, Layered Scaling, and Blocksize Debates | Lex Fridman Podcast #173
Lex Fridman
A Bitcoin protocol upgrade implemented in 2017 that laid the groundwork for the Lightning Network, resolving certain scaling issues and transaction malleability.

Alex Gladstein: Bitcoin, Authoritarianism, and Human Rights | Lex Fridman Podcast #231
Lex Fridman
A Bitcoin upgrade that enabled the Lightning Network, arising from the 'block size conflict' and representing an evolution in Bitcoin's architectural design.

Satoshi Nakamoto and the Civil-War Within Bitcoin
ColdFusion
Segregated Witness, an upgrade activated in 2017 to store transaction data more efficiently, allowing more data per block.