Even as late as the Middle Ages people slept naked until textile advances brought heavy long nightgowns (nightshirts) and nightcaps.
Nightshirts were a sleeping garment styled like a man’s shirt in mini, knee or calf length with rounded hem and a slash at the side seams.
Nightcaps were stocking caps made of knitted silk often with a tassel on top and provided warmth while sleeping. The nightcap could be used other than just for sleeping. In the 14th to mid 19th century it was a skullcap with an upturned brim worn indoors by men when their wig was removed. During the 19th century the nightcap was called a "jelly-bag".
Pajamas were introduced about 1880 from India for men to wear for sleeping instead of nightshirts.
The History of Silk: The legend is that in 2600 BC the Chinese princess Xi Liu Shi was drinking tea under a mulberry tree when a silk cocoon accidentally dropped into her tea. She discovered, as it slowly unraveled in her cup, that it consisted of one single thread. The Chinese began silk fabric production and sent the finished products to Europe. The Romans under Augustus Caesar loved silk. It was worth its weight in gold.
In the 6th century AD, two Persian merchants, disguised as priests, smuggled silkworm eggs out of China and presented them to Emperor Justinian in Constantinople. By the 12th century Italy was into silkworm breeding and production of fine silks.