To add decorative or savory touches to food.
A garnish is some sort of food accompanying another dish and complementing the flavour and appearance of that dish; a garnish can be as simple as a sprig of parsley or as elaborate as a ragout blended with sauce and poured into a pastry shell. In origin, the word garnish derives from the Old French word guarnir, meaning to protect or to provide with necessities. This was the meaning that garnish possessed when it first appeared in English in the fourteenth century, and it was used especially in relation to fortresses provided or “garnished” with arms and soldiers. Of course, more pleasant things can also be provided to someone, including items merely luxurious rather than necessary; accordingly; it was not long before garnish also came to mean to embellish. It was this sense of garnish that led to the word being used in the late seventeenth century as a name for a food item that complements or embellishes a main dish. Other words also developed from the Old French guarnir but stayed closer to its original sense of to provide; these include garrison (a fortress provided with a detachment of soldiers) and garage (a place where vehicles are provided with fuel and repairs). Incidentally, the garnish that refers to the action of seizing someone’s assets until he repays a debt is the same word as the culinary garnish: originally, this legal garnish meant to provide someone with an official writ warning him to pay up or suffer the consequences.