"the mark in the middle of the belly where the umbilical cord was attached in the fetus," Middle English navele, from Old English nafela, nabula, from Proto-Germanic *nabalan (source also of Old Norse nafli, Danish and Swedish navle, Old Frisian navla, Middle Dutch and Dutch navel, Old High German nabalo, German Nabel), from PIE *(o)nobh- "navel" (source also of Sanskrit nabhila "navel, nave, relationship;" Avestan nafa "navel," naba-nazdishta "next of kin;" Persian naf; Latin umbilicus "navel;" Old Prussian nabis "navel;" Greek omphalos; Old Irish imbliu). For Romanic words, see umbilicus.
The cords of all link back, strandentwining cable of all flesh. [Joyce, "Ulysses"]
"Navel" words from other roots include Lithuanian bamba, Sanskrit bimba- (also "disk, sphere"), Greek bembix, literally "whirlpool." Old Church Slavonic papuku, Lithuanian pumpuras are originally "bud." Considered a feminine sexual center since ancient times, and still in parts of the Middle East, India, and Japan. In medieval Europe, it was averred that "[t]he seat of wantonness in women is the navel" [Cambridge bestiary, C.U.L. ii.4.26]. Words for it in most languages have a secondary sense of "center."
Meaning "center or hub of a country" is attested in English from late 14c. To contemplate (one's) navel "meditate" is from 1933; hence navel-gazer (by 1947); see also omphaloskepsis. Navel orange is attested from 1831.
Another great key I will give you is to be found by the contemplation of the Manipur Lotus, which is in the navel, or thereabouts. By contemplating this center you will be able to enter and go into another person's body, and to take possession of that person's mind, and to cause him to think and to do what you want him to do; you will obtain the power of transmuting metals, of healing the sick and afflicted, and of seership. ["Swami Brahmavidya," "Transcendent-Science or The Science of Self Knowledge," Chicago, 1922]
Old English cnawan (class VII strong verb; past tense cneow, past participle cnawen), "perceive a thing to be identical with another," also "be able to distinguish" generally (tocnawan); "perceive or understand as a fact or truth" (opposed to believe); "know how (to do something)," from Proto-Germanic *knew- (source also of Old High German bi-chnaan, ir-chnaan "to know"), from PIE root *gno- "to know."
For pronunciation, see kn-. Once widespread in Germanic, the verb is now retained there only in English, where it has widespread application, covering meanings that require two or more verbs in other languages (such as German wissen, kennen, erkennen and in part können; French connaître "perceive, understand, recognize," savoir "have a knowledge of, know how;" Latin scire "to understand, perceive," cognoscere "get to know, recognize;" Old Church Slavonic znaja, vemi). The Anglo-Saxons also used two distinct words for this, the other being witan (see wit (v.)).
From c. 1200 as "to experience, live through." Meaning "to have sexual intercourse with," also found in other modern languages, is attested from c. 1200, from the Old Testament (Genesis iv.1). Attested from 1540s in colloquial phrases suggesting cunning or savvy (but often in the negative); to not know one's ass from one's elbow is from 1930.
As far as (one) knows "to the best of (one's) knowledge" is late 14c. Expression God knows is from c. 1400. To know too much (to be allowed to live, escape, etc.) is from 1872. To know better "to have learned from experience" is from 1704.
You know as a parenthetical filler is from 1712, but it has roots in 14c. You know as a euphemism for a thing or situation unmentionable is from 1867; you-know-who for a person it is thought best not to name (but implying the hearer knows) is from 1840.
As an expression of surprise, what do you know attested by 1914. Don't I know it in the opposite sense ("you need not tell me") is from 1874. You never know as a response to something unexpected is attested from 1924.
"a featherless plantigrade biped mammal of the genus Homo" [Century Dictionary], Old English man, mann "human being, person (male or female); brave man, hero;" also "servant, vassal, adult male considered as under the control of another person," from Proto-Germanic *mann- (source also of Old Saxon, Swedish, Dutch, Old High German man, Old Frisian mon, German Mann, Old Norse maðr, Danish mand, Gothic manna "man"), from PIE root *man- (1) "man." For the plural, see men.
Sometimes connected to root *men- (1) "to think," which would make the ground sense of man "one who has intelligence," but not all linguists accept this. Liberman, for instance, writes, "Most probably man 'human being' is a secularized divine name" from Mannus [Tacitus, "Germania," chap. 2], "believed to be the progenitor of the human race."
Specific sense of "adult male of the human race" (distinguished from a woman or boy) is by late Old English (c. 1000); Old English used wer and wif to distinguish the sexes, but wer began to disappear late 13c. and was replaced by man. Universal sense of the word remains in mankind and manslaughter. Similarly, Latin had homo "human being" and vir "adult male human being," but they merged in Vulgar Latin, with homo extended to both senses. A like evolution took place in Slavic languages, and in some of them the word has narrowed to mean "husband." PIE had two other "man" roots: *uiHro "freeman" (source of Sanskrit vira-, Lithuanian vyras, Latin vir, Old Irish fer, Gothic wair; see *wi-ro-) and *hner "man," a title more of honor than *uiHro (source of Sanskrit nar-, Armenian ayr, Welsh ner, Greek anēr; see *ner- (2)).
Man also was in Old English as an indefinite pronoun, "one, people, they." It was used generically for "the human race, mankind" by c. 1200. As a word of familiar address, originally often implying impatience, c.1400; hence probably its use as an interjection of surprise or emphasis, since Middle English but especially popular from early 20c.
As "a woman's lover," by mid-14c. As "adult male possessing manly qualities in an eminent degree," from 14c. Man's man, one whose qualities are appreciated by other men, is by 1873. Colloquial use of the Man for "the boss" is by 1918. To be man or mouse "be brave or be timid" is from 1540s. Meaning "piece with which a game (especially chess) is played" is from c. 1400.
Man-about-town "man of the leisure class who frequents clubs, theaters, and other social resorts" is from 1734. Man of the world is from mid-14c. as "secular man, layman;" by early 15c. as "man experienced in the ways of the world, one able to take things in stride." To do something as one man "unanimously" is from late 14c.
So I am as he that seythe, 'Come hyddr John, my man.' 
MANTRAP, a woman's commodity. [Grose, "Dictionary of the Vulgar Tongue," London, 1785]
At the kinges court, my brother, Ech man for himself. [Chaucer, "Knight's Tale," c. 1386]
Old English wicce "female magician, sorceress," in later use especially "a woman supposed to have dealings with the devil or evil spirits and to be able by their cooperation to perform supernatural acts," fem. of Old English wicca "sorcerer, wizard, man who practices witchcraft or magic," from verb wiccian "to practice witchcraft" (compare Low German wikken, wicken "to use witchcraft," wikker, wicker "soothsayer").
OED says of uncertain origin; Liberman says "None of the proposed etymologies of witch is free from phonetic or semantic difficulties." Klein suggests connection with Old English wigle "divination," and wig, wih "idol." Watkins says the nouns represent a Proto-Germanic *wikkjaz "necromancer" (one who wakes the dead), from PIE *weg-yo-, from PIE root *weg- "to be strong, be lively."
That wicce once had a more specific sense than the later general one of "female magician, sorceress" perhaps is suggested by the presence of other words in Old English describing more specific kinds of magical craft. In the Laws of Ælfred (c. 890), witchcraft was specifically singled out as a woman's craft, whose practitioners were not to be suffered to live among the West Saxons:
Ða fæmnan þe gewuniað onfon gealdorcræftigan & scinlæcan & wiccan, ne læt þu ða libban.
The other two words combined with it here are gealdricge, a woman who practices "incantations," and scinlæce "female wizard, woman magician," from a root meaning "phantom, evil spirit." Another word that appears in the Anglo-Saxon laws is lyblæca "wizard, sorcerer," but with suggestions of skill in the use of drugs, because the root of the word is lybb "drug, poison, charm" (see leaf (n.)). Lybbestre was a fem. word meaning "sorceress," and lybcorn was the name of a certain medicinal seed (perhaps wild saffron). Weekley notes possible connection to Gothic weihs "holy" and German weihan "consecrate," and writes, "the priests of a suppressed religion naturally become magicians to its successors or opponents." In Anglo-Saxon glossaries, wicca renders Latin augur (c. 1100), and wicce stands for "pythoness, divinatricem." In the "Three Kings of Cologne" (c. 1400) wicca translates Magi:
Þe paynyms ... cleped þe iij kyngis Magos, þat is to seye wicchis.
The glossary translates Latin necromantia ("demonum invocatio") with galdre, wiccecræft. The Anglo-Saxon poem called "Men's Crafts" (also "The Gifts of Men") has wiccræft, which appears to be the same word, and by its context means "skill with horses." In a c. 1250 translation of "Exodus," witches is used of the Egyptian midwives who save the newborn sons of the Hebrews: "Ðe wicches hidden hem for-ðan, Biforen pharaun nolden he ben." Witch in reference to a man survived in dialect into 20c., but the fem. form was so dominant by 1601 that men-witches or he-witch began to be used.
Extended sense of "old, ugly, and crabbed or malignant woman" is from early 15c; that of "young woman or girl of bewitching aspect or manners" is first recorded 1740. Witch doctor is from 1718; applied to African magicians from 1836.
At this day it is indifferent to say in the English tongue, 'she is a witch,' or 'she is a wise woman.' [Reginald Scot, "The Discoverie of Witchcraft," 1584]