heelyoudaoicibaDictYouDict[heel 词源字典]
heel: English has two separate words heel. The one that names the rear part of the foot [OE] comes ultimately from Germanic *khangkh-, which also produced English hock ‘quadruped’s joint corresponding to the human ankle’. From it was derived *khākhil-, source of Dutch hiel, Swedish häl, Danish hæl, and English heel. Heel ‘tilt, list’ [16] is probably descended from the Old English verb hieldan ‘incline’ (which survived dialectally into the 19th century), its -d mistaken as a past tense or past participle ending and removed to form a new infinitive. Hieldan itself came ultimately from the prehistoric Germanic adjective *khalthaz ‘inclined’.
=> hock[heel etymology, heel origin, 英语词源]
heel (n.1)youdaoicibaDictYouDict
"back of the foot," Old English hela, from Proto-Germanic *hanhilon (cognates: Old Norse hæll, Old Frisian hel, Dutch hiel), from PIE *kenk- (3) "heel, bend of the knee" (source also of 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."
heel (v.2)youdaoicibaDictYouDict
"to lean to one side," in reference to a ship, Old English hieldan "incline, lean, slope," from Proto-Germanic *helthijan (cognates: 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.
heel (n.2)youdaoicibaDictYouDict
"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).
heel (v.1)youdaoicibaDictYouDict
of a dog, "to follow or stop at a person's heels," 1810, from heel (n.1). Also see heeled.