From Ukcider

Chaptalisation to Raise Alcohol Content

Raising the SG and potential ABV by adding sugar is euphemistically called chaptalisation, though many purists would call it bastardisation... This is named after the 18th/19th century French chemist Jean-Antoine Chaptal, who suggested the addition of small amounts of beet sugar to wine musts in poor years when the SG was not high enough. This is still permitted under French wine law today, but only under strictly regulated conditions. Most commercial UK ciders are now made by gross chaptalisation of juice with glucose syrup to an SG of maybe 1.110. This gives a 'base cider' ca 14% alcohol, which is then diluted with water before retail sale.