Flips all share 3 common ingredients: egg yolk, sugar, and spirits. Many also add spices, and spiced flips were extremely popular in the 18th and 19th centuries.
A generic flip can be made by shaking an ounce and a half of spirits, an egg, and enough sugar to sweeten the drink.
It is likely the inclusion of the raw egg which has made flips less popular in the modern era. Although there have been no reported cases of salmonella poisoning from food prepared in a home, salmonella is a real danger when using raw eggs. If you are uncomfortable with the risk, then we recommend that you avoid flips and other drinks with raw eggs.