"back of the foot," Old English hela, from Proto-Germanic *hanhilon (cf. Old Norse hæll, Old Frisian hel, Dutch hiel), from PIE *kenk- (3) "heel, bend of the knee" (cf. Old English hoh "hock").
Meaning "back of a shoe or boot" is c.1400. Down at heels (1732) refers to heels of boots or shoes worn down and the owner too poor to replace them. For Achilles' heel "only vulnerable spot" see Achilles. To "fight with (one's) heels" (fighten with heles) in Middle English meant "to run away."
"contemptible person," 1914 in U.S. underworld slang, originally "incompetent or worthless criminal," perhaps from a sense of "person in the lowest position" and thus from heel (n.1).
"to lean to one side," in reference to a ship, Old English hieldan "incline, lean, slope," from Proto-Germanic *helthijanan (cf. Middle Dutch helden "to lean," Dutch hellen, Old Norse hallr "inclined," Old High German halda, German halde "slope, declivity"). Re-spelled 16c. from Middle English hield, probably by misinterpretation of -d as a past tense suffix.
The rounded posterior portion of the foot under and behind the ankle.
A similar anatomical part, such as the rounded base of the palm.
[last sense fr heel, ''arm a fighting cock with a gaff or spur,'' found by 1755]