- talus (n.1)
- "anklebone," 1690s, from Latin talus "ankle, anklebone, knucklebone" (plural tali), related to Latin taxillus "a small die, cube" (they originally were made from the knucklebones of animals).
- talus (n.2)
- "slope," 1640s, from French talus (16c.), from Old French talu "slope" (12c.), probably from Gallo-Romance *talutum, from Latin talutium "a slope or outcrop of rock debris," possibly of Celtic origin (cf. Breton tal "forehead, brow").
OED, however, suggests derivation from root of talus (1) in the sense of "heel" which developed in its Romanic descendants. Mainly used of military earthwork at first; meaning "sloping mass of rocky fragments that has fallen from a cliff" is first recorded 1830.