Pumpernickel means "devil's fart", a definition accepted by the publisher Random House, and by some English language dictionaries, including the Merriam-Webster Dictionary. The American Heritage Dictionary adds "so named from being hard to digest". A variant of this explanation is also given by the German etymological dictionary "Kluge" that says the word is older than its usage for the particular type of bread, and may have been used as a mocking name for a person of unrefined manners ("farting Nick") first. The change of meaning may have been caused by its use as a mocking expression for the (in the eyes
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"