Why do we say "Let Sleeping Dogs Lie"?

Meaning:

Don't stir up trouble

Background:

This proverb traces back to at least the late 14th century where it can be found in Chaucer's Troilus and Criseyde (c1374):
"It is nought good a slepyng hound to wake"

Those wishing to show off their erudition may wish to revert to the Latin equivalent which, one has to assume, came earlier: Quieta non movere (don't disturb the peace).

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