Floodgates

Large gates that control the flow of water in dams or channels; also used metaphorically to mean the release of something previously held back.

Compound of 'flood' (from Old English 'flod') and 'gate' (from Old English 'geat'). The term literally describes gates on water structures, but by the 1600s was used figuratively for any sudden release of pent-up things like emotions or information.