It's a load of dick.
The amount of songs which predominately feature the word 'yeah' is ridiculous.
And that's only the songs with only the word 'yeah'.
Doesn't even include 'yeh', 'yer' or 'oh yeah'.
Admittedly, back in the day my favourite song was a twelve-bar-blues where the lyrics were:
"Yeah" (x12) repeat as desired.
But then again, this was from a time when I thought that this was badass:
Now, I desire nothing more than for less songs to be about a word which simply is an agreement.
Now, I'd rather be on the Challenger Space Shuttle than listen to that song again.