breakneck adj.

Old English brecan "to divide solid matter violently into parts or fragments; to injure, violate (a promise, etc.), destroy, curtail; to break into, rush into; to burst forth, spring out; to subdue, tame" (class IV strong verb; past tense bræc, past participle brocen), from Proto-Germanic *brekanan (source also of Old Frisian breka, Dutch breken, Old High German brehhan, German brechen, Gothic brikan), from PIE root *bhreg- "to break."

Closely related to breach (n.), brake (n.1), brick (n.). The old past tense brake is obsolete or archaic; the past participle is broken, but shortened form broke is attested from 14c. and was "exceedingly common" [OED] 17c.-18c.

Of bones in Old English. Formerly also of cloth, paper, etc. The meaning "escape by breaking an enclosure" is from late 14c. The intransitive sense of "be or become separated into fragments or parts under action of some force" is from late 12c. The meaning "lessen, impair" is from late 15c. That of "make a first and partial disclosure" is from early 13c. The sense of "destroy continuity or completeness" in any way is from 1741. Of coins or bills, "to convert to smaller units of currency," by 1882.

In reference to the heart from early 13c. (intransitive); to break (someone's) heart is late 14c. Break bread "share food" (with) is from late 14c. To break ground is from 1670s as "to dig, plow," from 1709 in the figurative sense of "begin to execute a plan." To break the ice "overcome the feeling of restraint in a new acquaintanceship" is from c. 1600, in reference to the "coldness" of encounters of strangers. Break wind is attested from 1550s. To break (something) out (1890s) probably is an image from dock work, of freeing cargo before unloading it.

The ironic theatrical good luck formula break a leg (by 1948, said to be from at least 1920s) has parallels in German Hals- und Beinbruch "break your neck and leg," and Italian in bocca al lupo. Evidence of a highly superstitious craft (see Macbeth). According to Farmer & Henley, in 17c. the expression was used euphemistically, of a woman, "to have a bastard."

"that part of an animal body between the head and the trunk and which connects those parts," Middle English nekke, from Old English hnecca "neck, nape, back of the neck" (a fairly rare word) from Proto-Germanic *hnekk- "the nape of the neck" (source also of Old Frisian hnekka, Middle Dutch necke, Dutch nek, Old Norse hnakkr, Old High German hnach, German Nacken "neck"), with no certain cognates outside Germanic, though Klein's sources suggest PIE *knok- "high point, ridge" (source of Old Irish cnocc, Welsh cnwch, Old Breton cnoch "hill").

The more usual Old English words were hals (the general Germanic word, cognate with Gothic, Old Norse, Danish, Swedish, Dutch, German hals), from Proto-Germanic *halsaz, which is perhaps cognate with Latin collum (see collar (n.)); and sweora, swira "neck, nape," probably also from a PIE root meaning "column" (cognate with Old English swer "column," Sanskrit svaru- "post").

Oxen and other draught animals being yoked by the neck, it became a symbol of burdens, of submission or subjugation, and also resistance or obstinacy (compare stiff-necked). Figuratively, "life" (late 15c.) from the breaking or severing of the neck in legal executions. Meaning "narrow part at the top of a bottle" is from late 14c.; meaning "part of a garment which covers the neck" is from 1520s. Meaning "long, slender part of a stringed musical instrument" is from 1610s.

Sense of "isthmus, long, narrow strip of land connecting two larger ones" is from 1550s. Phrase neck of the woods (American English) is attested from 1780 in the sense of "narrow stretch of woods;" 1839 with meaning "settlement in a wooded region." To stick (one's) neck out "take a risk" is recorded by 1919, American English. Horses running neck and neck "at an equal pace" is attested from 1799; to win by a neck is from 1823. To be up to the neck "have a lot of" at first (mid-19c.) suggested "fed full," but since c. 1900 it has implied "in deep."