something very easily done.
Origin of child's play
Middle English word dating back to 1350–1400
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for child's play
informal something that is easy to do
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Idioms and Phrases with child's play
Something easily done, a trivial matter. For example, Finding the answer was child's play for Robert, or The fight we had was child's play compared to the one I had with my mother! Originating in the early 1300s as child's game, the idiom was already used in its present form by Chaucer in The Merchant's Tale: “It is no child's play to take a wife.”
The American Heritage® Idioms Dictionary
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