Pumpernickel an old Bavarian term for "hard", either referring to the process used to grind the grain into flour, or the density of the final bread product. According to "Langenscheidts Taschen Wörterbücher" (1956), it refers to a form of "pumping work". The philologist Johann Christoph Adelung states that the word has an origin in the Germanic vernacular where was a New High German synonym for being flatulent, and was a form of the name Nicholas, commonly associated with a goblin or devil (e.g. "Old Nick", a familiar name for Satan), or more generally for a malevolent spirit or demon. Hence, "pumpernickel"
What Love Is Made Of extremely positive about "What Love Is Made Of", describing it as "darker than anything" from "On a Mission", while calling it "slinky". The reviewer went on to commend the "irresistibly pouty" chorus. Pitchfork Media's Katherine St. Asaph commented that, in the song, the singer "sound[ed] completely enthralled, by either her lover or the music" and complimented her voice, noting that it seemed "ten times bigger than before". Jordan Sargent of "Spin" magazine called the track "exuberant" and highlighted Katy's vocal performance, which he deemed "typically fantastic", while the team from pop music website Popjustice gave "What Love Is Made Of"