In one of a series of interviews with MTV, Lamar talked about how the concept for "Butterfly" evolved and eventually got him to its final title. His working title: "Tu Pimp a Caterpillar."
That first word, he said, was an intentional nod to Tupac Shakur, who as we all know now, was "interviewed" on Lamar's "Mortal Man," the album's final track (Tupac's portions were sampled posthumously from an old radio interview).
And as for the changing insect life cycle reference? Lamar said he "wanted to show the brightness of life and the word 'pimp' has so much aggression, and that represents several things. For me, it represents using my celebrity for good. Another reason is, not being pimped by the industry through my celebrity."
For what it's worth, we think he made the right decision to call it "To Pimp a Butterfly," as his first idea for the LP title sounds like a much more noir sequel to this other classic work.