Dear Straight Dope: A Japanese student once asked the meaning of the phrase "sleep tight" (as in "sleep tight, don't let the bed bugs bite"). I have always been interested in word origins but I have yet to come across this one. I haven't even found anyone who could make a good guess. Can you help solve this riddle? Guy Nolan, Washington, DC

SDStaff Hawk replies:

There are two possible explanations for this expression. We’ll start with the one I personally like, because it’s a lot more interesting, and then we’ll get to what in all probability is the real one.

Explanation #1. Here in Cajun country where I live, before the days of mattresses, beds were square frames elevated from the ground, with ropes tied across in a sort of weave. It was similar to a hammock in concept. Anyway, in order to sleep well, the “mattress” couldn’t sag, so the bed had to be “tight.” (And free of bed bugs, but I thought that went without saying.)

For further insight I spoke to Dr. Jerry Lee Cross, a historian with the state of North Carolina. He confirms that the beds were, in fact, made of ropes tied across a frame. He adds that the origin of the phrase “sleep tight” is almost common knowledge among historians, simply because the modern bed is a little over a hundred years old.

But first a little about bedbugs. The 1996 Grolier Multimedia Encyclopedia, under “bedbug,” shows a critter not unlike a flea. Known to others as Cimex lectularius, this beast is a blood-sucker (literally). It is further described as nocturnal and capable of consuming its body weight in blood in five minutes. This one meal can provide nourishment for the insect for six months! This flat, oval, wingless bug measures about 0.6 cm long and produces irritating bites but is not known to carry disease. How comforting.

Dr. Cross’s wife, Carolyn, adds that she remembers her mother telling her stories about how she slept on such beds. Mrs. Cross recalls how her mother said she had to put the bedposts in small cans (like tuna cans) filled with kerosene, in a sort of moat-like fashion to keep the bedbugs from climbing into the bed (the bugs being wingless and all). Mrs. Cross also says that there were “rules” for sleeping: you couldn’t let the sheets hit the floor or have the bed too close to the walls, lest the bedbugs could climb into bed that way.

In Charles Panati’s Extraordinary Origins of Everyday Things (sorry, Cecil), he writes that mattresses were made of organic materials such as “straw, leaves, pine needles, and reeds” and tended to rot, mildew, and harbor rats and mice, who were hunting for bugs! Inorganic materials didn’t appear on the scene until about the 1870’s or so, when conical springs came into use. Cylindrical springs, which had been attempted earlier, had problems with no support, too much support, as well as spring failure from the poor metallurgical methods of the time. (Personally I say if it doesn’t have Magic Fingers, it ain’t a bed.)

The point is, when people used to say, “sleep tight, don’t let the bed bugs bite,” they weren’t trying to be cute. They meant it.

Explanation #2. That last one was a nice story, eh? Unfortunately, the Oxford English Dictionary, which knows a bit about such things, doesn’t buy it. Here’s what they say: “It seems that tight in this expression is the equivalent of the only surviving use of the adverb tightly meaning ‘soundly, properly, well, effectively’.”

I think anybody reading that would have to concede: It’s boring and unimaginative, and thus probably correct.

SDStaff Hawk, Straight Dope Science Advisory Board

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