You mean, Plant isn't putting emotion and Otis is? Wow, I always thought that putting effort into singing, in your personal way, achieving to express emotion was right, but I guess Plant should have sung it exactly like Otis so it would have expressed his feeling right?
Yes Dixon wrote this tune for Rush because of a relationship Rush was preoccupied with and it was the first hit on Cobra Records in 1956.... Petty obvious which came fist, just listen to the recording. We have to thank Zepplin and other British musicians for turning the US back on to our music.. so much was lost for many years. Several generations would probably have never heard this historical legacy of music.