Ring down the curtain
Bring something to an end.
The original and literal meaning of this phrase was 'to lower or close the stage curtain at the end of a theatrical performance'. Could this phrase just be a corruption of 'bring down the curtain'? It seems not. This term derives from the practice of ringing a bell to signal the time to close the curtains. The similarity between 'ring' and 'bring' is just coincidence. Curtains were also 'rung up' and this practice remains well-known to theatre-goers as 'the bell' which is rung to signal that a play is soon to begin or resume after an interval.
'Ring down...' Why 'ring'?
The earliest citation I can find for the phrase is from the celebrated English actor David Garrick, in his 1772 farce A Peep Behind the Curtain:
"Pray be so good as to ring down the curtain, that we may rehearse in form."
The figurative use, which just refers to the end of something, began use in the early 20th century; for example, this piece from Sheila Kaye-Smith's biography John Galsworthy:
"Thus the curtain rings down on Irene Forsyte, crushed under the heel of prosperity."