This idiom describes extreme generosity or selflessness, where someone would give even their own shirt to help another, symbolizing ultimate sacrifice. It conveys boundless compassion or charity, often used in personal or moral contexts to praise altruistic acts.

The phrase carries a tone of admiration, warmth, or idealism, reflecting cultural values of empathy and the human tendency to prioritize others’ needs. Its clothing imagery evokes a personal, tangible sacrifice, resonating in scenarios of aid or loyalty. The idiom celebrates selflessness, making it a heartfelt metaphor for unconditional giving.

The phrase likely originated in 18th-century Britain, rooted in Christian teachings of charity, as seen in biblical references to giving one’s cloak (Luke 6:29). Its earliest recorded use appears in Samuel Pepys’ diary (1660s), describing a man who ‘gave the shirt off his back’ to a beggar. The idiom gained traction in 19th-century literature, particularly in Charles Dickens’ *A Christmas Carol* (1843), which praised selfless acts. Its spread was amplified in the 20th century through charity campaigns and media, notably in *The Guardian* (1900s) for wartime aid. Its adoption across English-speaking cultures, especially in the U.K., U.S., and Canada, stems from its vivid imagery and universal appeal to kindness.