wrong side of someone
see under right side, on someone's.
What Does Calling Someone “Mom” On The Internet Mean?While Kim Kardashian was busy “breaking the Internet” with her controversial photoshoot for Paper in November of 2014, New Zealand singer/songwriter Lorde was teaching the world—or at least her Twitter and Tumblr followers—about a new slang use of the word mom.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.