https://www.youtube.com/watch?v=Q8Xaw72ESdA

According to researcher Danny Hatcher, the "Feynman Technique" was coined by Scott H. Young in the August 22, 2011 YouTube video Learn Faster with The Feynman Technique and the subsequent 2022-09-01 article Learn Faster with Feynman Technique, ostensibly in a summarization of Gleick, James (1992). Genius: The Life and Science of Richard Feynman. Pantheon Books. ISBN 0-679-40836-3. OCLC 243743850.

The frequently quoted Einstein that accompanies many instances of the Feynman Technique is also wrong and not said by Einstein.

The root Einstein quote, is apparently as follows:

that all physical theories, their mathematical expressions apart ought to lend themselves to so simple a description 'that even a child could understand them.' —Ronald W. Clark, p418 of Einstein: His Life and Times (1972)