But while many people may use the term footie pajamas, onesie or sleeper interchangeably, there can be slight differences between the garments. In general, a onesie or footie is a comfortable outfit while a sleeper is designed to keep baby warm during the night. For growing boys the distinction is less important as convenience largely carries the day, though boy footie pajamas are just as useful for young children as they are for infants.
Regardless of what you call it, the footie pajama has quite the history behind it. As best we can tell, footie pajamas started being used as far back as the 15th century. However, they really caught on in the late 19th century as "union suits" -- a sort of long underwear for women and men.
By the 1940s, union suits became "long johns," which then morphed into the blanket sleepers that we see today with the signature closed feet and padded soles. But it wasn't until an enterprising employee of the Michigan Central Woolen Company, Wiley Denton, created the first mass-produced boy footie pajamas called Dr. Denton's blanket sleepers.
Not only were the new garments perfect for the needs of kids during sleep, but children started to love wearing them throughout the day, too. The zipper hadn't been invented yet, so most footie pajamas still featured button closures, but once the zipper was added it took on the look and function that most of us today are familiar with.
In addition to kids that love the comfort and soft feel of boy footie pajamas, parents love them because they're much easier than a wardrobe of mismatched clothes and they always look great.