Through the years, pajamas have gone from nonexistent to ubiquitous, formal to casual, frilly to frumpy, and gender-specific to unisex. But these fluctuating fashions weren’t just caused by shifting style preferences; many were brought about by necessity, whether because of technology, war, or simple decorum.

1. MIGHTY WHITIES

There wasn't always a market for specific sleep clothing. From ancient times until the 1800s, people would either catch Zs in a variety of nightwear, ranging from their day clothing to undressing down to their tunic and undergarments—the equivalent of today’s plain white T-shirt and leggings. Because of this everyday barrier that people wore between their (very few) good outfits and their skin, clothing lasted longer.

For a long time, laundry was time consuming and difficult, and used harsh chemicals like lye. This is why, traditionally, briefs were white: they needed to be able to withstand all that boiling and bleaching, so there was no need to waste precious dyes on these hidden, over-washed items.

While today there are polka dots, plaid, and color prints splattered across all varieties of boxers and bikini cuts, you’ll still find some residual nostalgia when it comes to the fabric closest to our bums. Nearly every lingerie or intimates collection includes a set of stark white panties, and packages of white tees are a staple in any retail underwear section.

2. TOPLESS PAJAMAS: THE SEMANTICS OF SLEEPWEAR

The term “pajama” (also spelled “pyjama”) has roots in Persia and stems from the Persian word “paejama,” which refers a loose leg garment, usually held up with a drawstring. In the East, as early as the Ottoman Empire, men wore pajamas—usually made of Egyptian linen with a belted tunic—as standard attire. British colonists admired this casual style and by the 1870s they had adopted these roomy trousers as comfortable loungewear and, later, as sleepwear.

But by definition, the term referred only to the pants—so saying “pajama bottoms” was quite redundant. It wasn't until the 20th century that pajamas became associated with the coordinated ensemble comprising of a loose-fitting top and bottom. In fact, the word lost its specificity over the years, becoming interchangeable with any kind of sleepwear.

The pajama suits we know today were a “man thing” for much of their early existence. Only in the 1920s did American women begin to take a passing interest, but perhaps it was the moving pictures that made these silky sleep suits appealing to the masses of misses. According to American Pop Culture Decade by Decade by Bob Batchelor, the 1934 romantic comedy It Happened One Night sparked a craze for men's-style PJs when Claudette Colbert’s character wore a pair of pajamas borrowed from Clark Gable’s character.

3. THE VICTORIAN ERA: FORMAL (UNDER)WEAR

Circa 1923. Getty

Early nightshirts were shapeless, plain and practical, but by the mid-1800s, sleepwear started to become tailored and stylish: new cuts, new fabrics, new colors. Through this era, ankle-length chemises and nightgowns were prominent (the mid-calf and baby-doll style nighties came much later). During this time, many practical accessories complemented the bedtime wardrobe, depending upon social class, of course.

It was not uncommon for a wealthier woman to spend half the day in her nightclothes; doing so was not just comfortable, but it also helped preserve her more formal attire. When she accepted guests, attended a meal or took a stroll through the garden, she’d often wear a dressing gown over her nightdress. This garment, as its name would imply, also protected a lady’s clothes from hair powder while she sat at her vanity, getting ready for the day. In colder temperatures, prior to going to bed or just upon awakening, a night jacket—shorter than a dressing gown—would be worn atop nightclothes.

A 1950s model in a nightdress, looking at a dressing gown. Getty

Men followed a similar layering practice; they too had longer robes available. Also, shorter smoking jackets protected day clothes and nighttime attire, allowing men to still appear elegant when entertaining evening guests.

In the early- and mid-20th century, the idea of wearing a covering over bedclothes was still common and the flowing jackets gained popularity as they provided women a way to still look fashionable when answering the door or winding down at home in the evening.

4. HEADS UP: NIGHTCAPS HAVE A POINT

Circa 1905. Getty

Some say that people wore nightcaps to protect themselves from lice, but that theory has been largely debunked. Typically, bedrooms were not heated, so it was important to bundle up for the night. No one wants to suffocate in their sleep, so burying heads under the covers wasn’t the most optimal solution. The nightcap, therefore, became a viable option for keeping one's head warm, and its long, pointy tip allowed the extra flowing fabric to double as a scarf. Call it an early life hack.

Nightcaps have other uses too. For example, in the Victorian era, if a lady had to rise early and meet people before her tresses were properly fashioned, she’d wear her bonnet-style sleeping cap along with her dressing gown to breakfast. Additionally, in the early 20th century, women generally only styled their hair once or twice a week, and sleeping in a cap would preserve the hairdo. Today, various forms of nightcaps still have relevance. Many women with Afro-textured hair sleep with scarves and wraps to protect their twists or braids, and hair professionals often recommend that those with brittle hair wear a satin head covering to bed to prevent breakage.

5. COVERS YOU CAN'T KICK OR STEAL

Footie pajamas sure are cute, but they’re also quite practical. First mass-produced by Michigan-based company Dr. Denton Sleeping Garment Mills in the 1860s, the “blanket sleeper” was marketed as “covers that can’t be kicked off.” They assured parents that even during the chilliest of weather, children would stay bundled up all night, tucked in or not, because the pajamas were actually made from a thick, warm, blanket-like material.

These romper suits, as they often were called, had vinyl feet to prevent slips while, well, romping. Denton’s also came with fold-down sleeves with drawstrings to cover the hands, and some styles offered hoods. The earliest versions closed with snaps or buttons, predating the less drafty head-to-toe zippers we know today. And, perhaps the most iconized feature of the classic footie pajama: the drop seat. This butt flap, available in some styles, allowed wearers to go to the bathroom without removing the entire garment.

While most often associated with children, the blanket sleeper came in sizes for all ages. In fact, this “onesie” was said to be inspired by the union suit: a one-piece, often red flannel undergarment that was the predecessor to the long johns we know today. It was aptly named: it united a top and a bottom.

During the energy crisis in the 1970s—when Americans were likely not turning up the heat as high at night—blanket sleepers saw a spike in sales. Today, one-piece PJs are still widely available, but are considered more of a novelty (unless, of course, they're being worn by a child, in which case they are still incredibly popular).

6. CLOSE QUARTERS

Lonnie Donegan once asked, via his catchy song, “Does Your Chewing Gum Lose Its Flavour (On the Bedpost Overnight?).” But this furniture feature is more than a temporary home for a wad of Wrigley’s. See, our sleeping quarters once worked hand-in-hand with our evening attire to make for a comfortable night’s rest. Bedposts, much like nightcaps and blanket sleepers, created warmth. The tall posts anchored fabric drapes, which, when pulled together, made an insulated napping nook that shielded the sleeper from the cold.

These enclosed spaces also created a bit of privacy for, you know, those moments when pajamas weren't necessary. But as technology advanced and homes became warmed by central heating, bedposts and canopies lost some of their "flavor," as they became less utilitarian and more of a home décor fashion statement.

7. PAJAMAS TO GO: SLEEPWEAR AS OUTERWEAR

An editorial photo from the 1960s. Bess Georgette via Flickr // CC BY-SA 2.0

In the 1940s—during wartime—the “kangaroo pockets” often sewn into women’s housecoats took on a new function. This feature, according to costume website Vintage Dancer, would allow women to grab and stash a few important belongings (presumably, should she need to leave quickly and unexpectedly in the middle of the night). 

Today, it’s seemingly acceptable to run quick daytime errands while donning nighttime attire. At least, depending upon who you ask. A British school headmaster recently sent a memo home to parents putting the kibosh on wearing pajamas while dropping off children at school in the morning, and a judge in Pennsylvania gave the same order to people showing up for court. But what if you can’t tell the difference? There is now a growing market for extremely comfortable clothing that looks appropriate in public. Lines like Bammies (a portmanteau of business and jammies) offer slick-yet-soft office attire, while novelty item the Suitsy is a one-piece sleeper designed to look like a suit.

But while sleepwear has certainly evolved along with social customs and technology, remnants of traditions past still show up on display in department stores and in fashion catalogs. And if you’ve ever dozed off on the couch fully clothed after an exhausting day, rest assured: this isn’t lazy. By not changing clothes, you’re simply adhering to a long-forgotten nighttime trend.