@icedquinn

The quote actually originated with Rutherford and was later repeated in another form by Einstein, feynman adopted it as a technique.

Rutherford said "it should be possible to explain the laws of physics to a barmaid."

Einstein said, while referencing Rutherford in a conversation with de Broglie in france: "that all physical theories, their mathematical expressions apart ought to lend themselves to so simple a description that even a child could understand them."

So Einstein coined the phrase and idea in reference to a child.

The Feynman technique was explicitly inspired by Einstein and is a 4 step technique:

1) Pick the subject of interest
2) explain the concept as if to a 6th grader
3) Identify the holes in your understanding
4) Study the parts you couldnt explain simply

While the Feynman technique is based off observations in Feynmans study habits he never taught the technique formally nor did he define it.

@lucifargundam @TechUr