The term 'Rickey Ingredient' refers to the two main ingredients used in a Rickey cocktail, which is a type of mixed drink. The two ingredients are LIME and GIN, with LIME being four letters and GIN being three letters. LIME is a citrus fruit that is widely used in many cocktails and other drinks, while GIN is a type of distilled alcoholic beverage made from juniper berries. Together, these two ingredients make up the classic Rickey cocktail.