noun 1 : fermented apple juice often made sparkling by carbonation or fermentation in a sealed container 2 : the expressed juice of fruit (such as apples) used as a beverage or for making other products (such as applejack)
In Middle English, the forms sider, sedyr, and cidre all referred to what we now call "cider" (specifically hard cider) or to alcoholic drink generally, as referenced in Biblical translations and related works. English got the word from Anglo-French, the particular kind of French used in medieval England. The Latin ancestor of the French word is sīcera, meaning "alcoholic drink"; sīcera and its lexical offspring likely referred to the fermented juice of apples (and other fruits) found in monasteries, and particularly in monasteries in areas of Europe that were not wine-producing.
The modern word cider dates to the 13th century and originally referred only to the fermented kind. When the non-fermented kind of cider became popular, the term hard cider was required to differentiate the two, making it a proper retronym that dates back to the late 18th century.