White from coronet to and including the fetlock is known as a _________ leg marking.

The correct answer refers to a specific type of leg marking on horses, known as an "ankle" marking. This marking is characterized by white that extends from the coronet (the area where the hoof meets the skin) to the fetlock joint.

An "ankle" marking is defined in this way because it is a more limited area of white compared to other markings. In contrast, a "half stocking" typically refers to a marking that covers the leg from just below the knee or hock to partway up the leg, while a "full stocking" covers a larger portion of the leg, often all the way to the knee or hock. The "pastern" marking, on the other hand, is usually limited to the area just above the hoof, below the fetlock, and does not extend as high as an "ankle" marking.

By identifying the specific region covered by the white marking, it becomes clear why "ankle" is the most accurate term for the description given in the question.