Shrub

In terms of mixed drinks, shrub is the name of two different, but related, acidulated beverages. One type of shrub is a fruit liqueur that was popular in 17th and 18th century England, typically made with rum or brandy and mixed with sugar and the juice or rinds of citrus fruit. The word shrub can also refer to a cocktail or soft drink that was popular during America's colonial era, made by mixing a vinegared syrup with spirits, water, or carbonated water. The term can also be applied to the base, a sweetened vinegar-based syrup from which the cocktail is made; that syrup is also known as drinking vinegar. Drinking vinegar is often infused with fruit juice, herbs and spices, for use in mixed drinks. The early English version of the shrub arose from the medicinal cordials of the 15th century. The drink gained popularity among smugglers in the 1680s trying to avoid paying import taxes for goods shipped from mainland Europe: To avoid detection, smugglers would sometimes sink barrels of spirits off-shore to be retrieved later; the addition of fruit flavours aided in masking the taste of alcohol fouled by sea water. [unreliable source?] An early Rum Shrub recipe from The English and Australian Cookery Book called for almonds, cloves, cassia, and the peel of oranges, "infused in the best rum," with the addition of a thread of ambergris and vanilla. "Good shrub is very delicious, and were it fashionable it would obtain rank as a liqueur."

Source: Wikipedia