The advent of this term would appear to coincide with the debut of rap group 'Outkast' - 'Hey Ya' single. With the popularity of the "shake it" lyrical section. This may also have to do with an Elvis song about being 'All shook up'.
To be 'shook' has other definitions as well including:
1. To be frightened
2. To be unwell mentally or physically
3. To be physically jarred
4. To be outmaneuvered in sports
5. To be in love (As per Elvis)
And the 'max' could be applicable to any of these definitions as well. However, the most common appears to coincide with dancing or being in love.
*Naw, honey, I can't shake it no mo' - I be max shook, baby
*After that scary movie, I'm max shook.