'Simpsons' Duff Beer Named For Lazy Oafs, Not Roses Rocker

Guns N' Roses bassist Duff McKagan is convinced "The Simpsons" named Springfeld's fave brew after him, but his theory is flat, 'cause Duff Beer was coined for a whole different reason ... TMZ has learned. Here's the deal ... the rocker recently told Stereogum he is, indeed, Duff Beer's namesake ... going so far as to say the show reached out back in the day to clear it, and he's bent out of shape he got cut out…