a public lavatory for men.
What’s The #’s Real Name?A hash has referred to stripes on military jackets since as early as 1910. But, in the 1980s, people started using hash to refer to the # symbol.
Origin of men's room
An Americanism dating back to 1925–30
Also called men's lounge.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for men's room
mainly US and Canadian a public lavatory for men
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012