The story
From the song It Ain't the Meat (it's the Motion) by Lois Mann and Henry Glover, written in 1951 and recorded by The Swallows. Often mistakenly attributed to Maria Muldaur, who sang a cover of the song on her 1974 album Waitress In The Donut Shop.
Etymology from Wiktionary, CC BY-SA 4.0.