It began as a preventive dose against seasickness and illness for fishermen heading out to sea, not as a party drink.
Madeira's local sugarcane rum is muddled with honey and fresh citrus (often orange, lemon or passion fruit) using a wooden muddler called a caralhinho, until frothy. Sold at beach bars and street stands, especially in the fishing village of Câmara de Lobos.
Why it's made this way: The drink evolved from 'panch,' a spiced drink Portuguese sailors encountered in India and adapted using Madeira's own sugarcane rum and citrus, and fishermen in Câmara de Lobos are still credited with popularizing it as a warming ritual before heading out.