Strolling down the streets of colonial Williamsburg, you wouldn’t have done a double take if you passed a gentleman clad in a flowing dress that looked like a nightgown. In fact, you might have complimented his fashion sense.

The garment was called a banyan, and in 18th century America and England it was considered typical, informal day wear for educated men of leisure. As comfortable and forgiving as sweatpants are today, banyans were loose robes that provided a welcome relief from the period’s often-constricting coats.

To modern sensibilities, banyans looked like nightgowns, or even bathrobes. In fact, they were originally inspired by styles from Japan, China, and India, which at the time had become fashionable in England thanks to the Dutch East India Company. (The name “banyan” is actually an Anglicized version of a Gujarati word for “trader.”)

Even though they were “casual” clothing items, some banyans were fancier than others. Fabrics ranged from simple linens and cottons to more elaborate chintz fabrics, brocades, and silks. There were also stylistic variations—fitted vs. loose, ties vs. buttons, and set-in sleeves vs. a chemise cut. Some banyans were quilted and lined, yet others were cool and lightweight. Patterns and colors also ranged widely. The variations were just about endless.

A banyan was worn over a shirt and breeches; a small, matching hat called a “negligé cap” topped off the look and kept a man's bald head warm when it wasn't covered by a wig. The oufit was commonly worn in the privacy of a gentleman’s home—particularly in the early morning or evening hours, during which he’d dine with his family, write letters, and read books.

However, banyans were also worn in public. Men in colonial Virginia donned banyans during the humid summer months. And since the loose cuts were thought to be conducive to “the easy and vigorous exercise of the faculties of the mind,” intellectuals like Benjamin Franklin and Sir Isaac Newton were often painted wearing banyans.

So if you’re passing through a museum and catch sight of an 18th century oil painting depicting a man wearing a silk gown, don’t think he stole it from his wife’s closet. The outfit may look silly now, but back then the ensemble signified that an individual was well-read, cosmopolitan, and refined—the same way that an expensive Polo shirt or a pair of imported designer spectacles might today.