Ankle comes from the Latin angulus (little corner or angle; hook-like) for the bend between the foot and the leg.
Angulus may also be the source for the Latin word angeion, small blood vessel, perhaps in reference to the frequent branching of such. Angeion gives us the combining form angio-, blood vessel, as in angiogram, angiogenesis, and angiotensin.
Non-anatomical tidbits: another word derived from angulus is Angul, the name given to the hook-shaped bit of land in what is now the Netherlands. From this area came the Angles, who along with the Saxons and Jutes, formed the Anglo-Saxons, the people who inhabited the land now called England in the 500 years prior to the Norman invasion of 1066.
An angler, one who fishes (with hooks), is also derived from angulus.
Picasso, Foot, 1894, Charcoal and crayon on paper, Museu Picasso, Barcelona, Spain.