A "lacquer head" is someone who gets high from sniffing paint, glue or other toxic substances (lacquer, which is a wood finish, will also do the trick). The song paints a bleak picture for young people addicted to inhalants, as Les Claypool
sings about a girl who gets hit by a truck after sniffing turpentine and a kid who goes into a coma after huffing carburetor cleaner.
Like just about every Primus song, it's delivered with a wink and in no way glorifies the characters in the song. Still, Claypool clarified that it "addresses the dangers of chemical abuse."