This idiom describes someone who is acting crazy, irrational, or out of touch with reality, as if fallen off a rocking chair in a fit of madness. It conveys mental instability or eccentricity, often used in personal or social contexts to question sanity humorously. The phrase carries a tone of surprise, mockery, or concern, reflecting cultural values of rationality and the human tendency to label odd behavior. Its furniture imagery evokes a comical loss of balance, resonating in scenarios like bizarre actions or decisions. The idiom playfully questions sanity, making it a quirky metaphor for irrationality.

The phrase originated in late 19th-century America, possibly tied to rocking chairs symbolizing calm, with falling off implying disruption, as noted in *Harper’s Magazine* (1890s). Its modern use emerged in the early 20th century, with *The Chicago Tribune* (1920s) using it for eccentric behavior. The idiom gained traction in the 1930s, amplified by radio comedies and slang, notably in *The Three Stooges* shorts. Its adoption, primarily in the U.S., stems from its vivid imagery and applicability to oddity, with some use in the U.K. and Australia.