This song is going on twenty years old at this point. I particularly enjoy the early-90s loping funk of it all (Jeff Ament's bass is especially notable).
Pearl Jam lyrics are often hard to decipher (ex: Yellow Ledbetter) but I had heard "Frank" enough times to understand the gist: that the song was about a killer who ate his victims ("Dirty Frank Dahmer / he's a gourmet cook, yeah"), although the tone is goofy & not serious (ex: Shaft joke).
I couldn't have pieced together the entire narrative without the invaluable resource that is pearljam.com. From reading the official lyrics the complete story is that of Frank Dahmer, imagined tour bus driver for Eddie & the band. The song is written from the point of view of Vedder about how his insane tour bus driver is in fact a cannibalistic serial killer luring victims under cover of the nation-wide tour ("Wanted a pass / so she relaxed. // Now the little groupie's gettin' / chopped up in the back").
I know the single was released in the US as a b-side to "Even Flow" & later on the 2003 Lost Dogs compilation. I wonder if the grim subject matter has anything to do with its relative anonymity.