What Makes a Dirty Martini 'Filthy'?

One point of particular confusion: What's the difference between a plain old Dirty Martini and a Filthy Martini?
To put it in the simplest terms possible, a Filthy Martini takes the classy Dirty cocktail to Flavortown. Ordering a Martini “Extra Dirty” or “Filthy” adjusts the cocktail’s recipe to include a higher ratio of salty olive brine in the drink. The Filthy Martini hones in on the olive brine’s distinct taste in an otherwise Dirty Martini and turns it up to the max.

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