A popular drink in the Caribbean, shandy was introduced by the British and dates back to at least the late 19th century. It's an icy cold mixture of equal parts beer or ale and ginger beer (sometimes ginger ale). Shandygaff, the original form of the word, is thought to come from the London vernacular for a pint of beer ("shant of gatter")shanty being a public house, gatter being an idiom for "water."
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.