Final answer:
The base alcohol used in the original Martini was gin, which became a popular spirit after distillation practices spread in the 15th century.
Step-by-step explanation:
When Martini cocktails gained popularity, particularly during the early 20th century, the base alcohol predominantly used was gin. The classic Martini was a simple concoction, comprising gin as the primary base spirit along with a small quantity of dry vermouth. This iconic cocktail, known for its sophistication and simplicity, relied on the botanical flavors of gin to create its distinct taste profile. Over the years, variations emerged, including the Vodka Martini, substituting gin with vodka as the base spirit. However, the original Martini cocktail, synonymous with elegance and refinement, originated with gin as its key ingredient, contributing to its enduring legacy and status as a timeless classic in the world of mixology and cocktail culture.