Today, my three year old son was doing something he wasn't normally supposed to do but we were letting him get away with it (wearing a backpack to the dinner table). He pointed out that he wasn't supposed to wear it and my wife replied that "today, we're just going to let that slide." Since he's young, the expression (obviously) didn't make sense to him. We explained that it meant that we were going to excuse the infraction today because it wasn't something that was terribly important. He then asked why "let it slide" means that. My wife and I didn't have an answer.
So, I'm here. Where does the expression "let it slide" come from? Why does it mean what it means? And so forth?
Best Answer
ODO's entry for slide defines "let something slide" as:
Therefore, the connotation is quite literal in that you are letting something slide down. Furthermore, there is also an implicit restriction involved in your expression which would expand to something along the lines of:
In other words, you're allowing the situation to deteriorate temporarily.
The etymology of the word slide dates the first use of let (something) slide to the 14th century: