Where did the term "Pound for Pound Best fighter in the world" come from?

Question

Where did the term "Pound for Pound Best fighter in the world" come from?

Answer 1

It was first used for weight lifters/body builders. Some decades ago a 7 year old could bench over 180 pounds. His parent claimed he did take supplements, but no physical enhancers. He was pound for pound(p4p) the strongest person on Earth. It later went into sports like basketball and soccer, then other sports and fighting.

Answer 2

from Ray Robinson, Ali was the greatest, but Robinson was the greatest pound 4 pound boxer, it started with him