child's play

American  

noun

1. something very easily done.

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child's play British  

noun

1. informal something that is easy to do

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child's play Idioms  

1. 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.”

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Etymology

Origin of child's play

Middle English word dating back to 1350–1400