be born yesterday

be + born + yesterday

be born yesterday (past tense only)

1. (informal) To be new, naive, innocent, inexperienced, or easily deceived.

   I was not born yesterday, you know. I have done this before!

   • 1840, Henry Cockton, chapter 60, in The Life and Adventures of Valentine Vox, the Ventriloquist, page 508:

     "Do you think," he added, with an ironical grin, "that you'll go for to gammon me into that air! I'm hinnocent, I know, but I wasn't born yesterday exactly."

   • 1915, William MacLeod Raine, chapter 6, in Steve Yeager:

     "Say, do I look like I was born yesterday? See any green in my eye, Cactus Center?"

   • 1998, Gwyn Hyman Rubio, Icy Sparks‎, page 155:

     "Compared to me, you were born yesterday."

   • 2005, Howard Zinn and Donaldo Pereira Macedo, Howard Zinn on Democratic Education‎, page 69:

     If you don't know important things about history, then it's as if you were born yesterday.

• Mostly used in the negative to indicate that one is not as naive as had been implied, but sometimes in an affirmative form, as in most of the quotations above.

• See Thesaurus:naive
• come down in the last shower (NZ, Australian)