big-boy pants

• big boy pants

From big boy.

big-boy pants pl (plural only)

1. (informal) Pull-up underwear worn by a boy during and after toilet training, as contrasted to the diapers worn during infancy.
   • 1983, Randall Wallace, So Late Into the Night, Doubleday, published 1983, →ISBN, page 29:

     Taking the baby from Kidd she snatched the screaming Davey by the wrist and half-carried him up the stairs yelling, "You wanna wear big-boy pants? Big boys wear big-boy pants, but big boys use the potty!"

   • 1987, Eleanor Weisberger, When Your Child Needs You: A Parents' Guide Through the Early Years, Adler & Adler, published 1987, →ISBN, page 31:

     "And so," you continue, "I'm putting your diapers away because you can now wear big boy pants and do your poop and pee-pee in the potty chair all by yourself."

   • 2000, Timothy A. Buzzard, Guru in a Little Boy Suit‎, Trafford Publishing, published 2000, →ISBN:

     “We've switched to big-boy pants. No more diapers,” his mom said a little too loud, so Alec would hear.

2. (informal, figuratively) A notional pair of trousers or underwear worn by a male when acting maturely.
   • 2011, David H. Hoffman, "Ugly election rhetoric" [letter to the editor], Suburban Life, 25 May 2011, page A8:

     If Horwitz is planning on running for office again in the future (and it certainly looks that way), perhaps it's time he put on his big-boy pants and engage in civil discourse.

   • 2012 April 12, Alissa Gulin, “Keystone Pipeline: It won't unlock the future”, in The Diamondback, volume 102, number 125, University of Maryland, page 4:

     He needs to put on his big boy pants and make the tough choice.

   • 2014, "Jewish Community Football League Playoffs and Championship!", The Baltimore Jewish Home, 11 December 2014 - 25 December 2014, Volume 1, Issue 21, page 19:

     Even with a broken finger, Wach put on his big boy pants, wrapped his hand, and dominated on the offensive line all game.

• big-girl pants

• in short pants