A gown, from the Saxon word, gunna, is a usually loose outer garment from knee-to-full-length worn by people of all genders in Europe from the Early Middle Ages to the 17th century, and continuing today in certain professions; later, the term gown was applied to any full-length woman's garment consisting of a bodice and an attached skirt. A long, loosely fitted gown called a Banyan was worn by men in the 18th century as an informal coat.
American silk and cotton ball gown, circa 1860, Metropolitan Museum of Art
A skirt is the lower part of a dress or a separate outer garment that covers a person from the waist downwards.
Skirt
Sumerian man wearing a kaunakes, c. 3000 BC
Statue of Ramaat, an official from Giza wearing a pleated Egyptian kilt, c. 2250 BC
Drawing of a girl's skirt made of wool yarn found in a Bronze Age tomb in Borum Eshøj, Denmark