the.com/tinderbox

means A place, group, or situation primed for sudden conflict or disaster, needing only a small trigger to set it off.

from Comes straight from the literal object: a small box holding tinder, flint, and steel that people once carried to strike sparks and start fires before matches existed. Because it held everything needed to burst into flame at a moment's notice, 'tinderbox' became the natural metaphor — by the 1800s it was being used for volatile political situations and powder-keg regions, the physical fire-starting kit turned into a figure of speech for anything one spark away from igniting.