Lose the shirt off one's back

Origin

In the smoky, high-stakes card rooms and back-alley gambling dens of the 19th century, fortunes were won and lost with terrifying speed. A desperate player, staring at a losing hand, might wager his last coin, then his watch, his boots, and finally, in a fit of wild despair, the very shirt on his back. This stark image of utter destitution, stripped of every possession down to the most basic garment, cemented the phrase into common language. It perfectly captured the catastrophic financial ruin where one literally had nothing left but the threadbare fabric clinging to their skin.