So THAT's Why We Say 'Night Night, Sleep Tight'

Though last year’s mass bed bug invasion may have led most of us to understand the second half of the phrase, I’m willing to bet you’re not 100% certain on why we say “Night night, sleep tight.” 

I, for one, had a sort of half-formed idea that it had something to do with trussing yourself up in tourniquet-like hotel duvets; I wondered whether maybe it had something to do with keeping your eyes shut tight, too. 

But recently, TikToker @notmrspock suggested we were all wrong. In a recent video, the creator responded to a commenter’s question as to where the phrase came from. 

“That’s an easy one,” he replied in the clip. 

Why do people think we say it?

“In Medieval times, beds used to ― instead of having springs, they would have ropes underneath them to put eh mattress or sack on,” the TikToker said. 

“If the ropes were slack, the bed would really sag. So what would you do? You’d tighten up all the ropes so you have a nice, firm base to lay on,” the creator added; hence the expression, he suggested. 

It’s a common story, appearing in Quora responses and BBC shows alike.

Is that true?

Rebecca Karstensen, Wylie House Museum Assistant and Docent for Indiana University, Bloomington, seemed to only partly agree with this assessment. 

While it’s true that beds in the 16th century did use ropes, which did need to be tightened, the first recorded use of the phrase didn’t come until 1866 ― a while after the invention of the coil mattress, which took over rope beds rapidly. 

“Goodbye little Diary. ‘Sleep tight and wake bright,’ for I will need you when I return,” the text reads, suggesting the term may have come about long after mos people used rope bedding. 

So, the researcher looked into the origin of the word.

“According to the Oxford dictionary, the closely related adverb ‘tightly’ can also mean ‘safely’ or ‘soundly’,” the researcher found.

This would not only explain the phrase’s use to this day, but also seems to align more closely with what most people instinctively think of when we hear it.

“Since it sounds a bit catchier and poetic to say two one-syllable words as ‘sleep tight’ instead of the awkward 3-syllable ‘sleep tightly,’ that might explain why the suffix –ly was dropped from the word,” she added. 

Writing for Cambridge’s Varsity publication, Georgie Thorpe points out that “The other issue is that it doesn’t quite make sense to tell someone to sleep tight when it’s their bed that needs to be tight, not them.” 

So, though the rope beds are fascinating, “sleep tight” likely stuck around because it sounds pretty cosy ― and also rhymes with “night.” 

Hey, not every fact can be as mind-blowing as the realisation that you cannot physically melt a Flake bar...