This saying suggests that when an old problem is no longer causing anyone trouble, it might be better left undiscussed: "Possibly he cohabited with Miss Bloggs, but don't mention it in front of his wife, let the sleeping dogs lie",[1] and dormant controversies should not be restarted even if they were never resolved.
[4] An early version in Middle English: "It is nought good a slepyng hound to wake" belongs to Chaucer (c. 1385 AD, "Troilus and Criseyde", III.764)[2] and is predated by earlier French: n'ésveillez pas lou chien qui dort, "wake not the sleeping dog" (early 14th century).
[5] The Chaucer's character, Pandarus, when uttering the phrase, is speaking literally, referring to Criseyde's ladies sleeping outside her chamber.
[2] Widespread use in the 20th century (see Bryan and Mieder[7] for some literary sources) made the proverb very recognizable, enabling some significant modifications, from "It is my policy to let sleeping senators lie" (Gore Vidal attacking his opponent Senator S. I. Hayakawa who was prone to napping in the chamber)[8] to “let sleeping dogmas lie” (Edmund Gosse).
[11] German: schlafende Hunde wecken ("to wake the sleeping dogs") is to create an inconvenience to oneself by attracting attention.