Where did the word restroom come from? Perhaps it would be funny to joke that people were too busy reading their favorite book or daily newspaper on the toilet, and they did not want to get up while in the middle of a cliffhanger. Hence, they were technically "resting" in the bathroom. However, while perhaps that idea has kept the word alive, that is not the true origin of the word "restroom" by any means.

The word "restroom" was originally used to refer to a public toilet only. A public toilet may sound rather rather disgusting; however, it is technically what everyone uses when they go to the bathroom in a school, movie theater, mall, or any other type of public place. The first usage of this term began around the turn of the 20th century in America.
In terms of toilet lingo, the word "restroom" is rather vague, as many other terms for the bathroom have more of an exact history. Nevertheless, the word "restroom" is thought to have originated from some of the definitions of the word "rest" such as "repose" or "refreshing one's self." We need not get into how those definitions directly relate to the activities that occur in a bathroom!
A variation of the word, retiring room, appeared in the upper crust of British society in the 1930s.
There's a plethora of names for the bathroom, including the toilet, washroom, water closet, lavatory, latrine, and many more. Don't get too hung up on what you choose to call it though. Remember, they are all just euphemisms, and everyone knows what really goes on behind the closed doors of the bathroom!