c. 1200, lafdi, lavede, from Old English hlæfdige (Northumbrian hlafdia, Mercian hlafdie), "mistress of a household, wife of a lord," apparently literally "one who kneads bread," from hlaf "bread" (see loaf (n.)) + -dige "maid," which is related to dæge "maker of dough" (which is the first element in dairy; see dey (n.1)). Also compare lord (n.)). Century Dictionary finds this etymology "improbable," and OED rates it "not very plausible with regard to sense," but no one seems to have a better explanation.
The medial -f- disappeared 14c. The word is not found outside English except where borrowed from it. Sense of "woman of superior position in society" is c. 1200; that of "woman whose manners and sensibilities befit her for high rank in society" is from 1861 (ladylike suggesting this sense is attested from 1580s, and ladily from c. 1400). Meaning "woman chosen as an object of chivalrous love" is from early 14c. Used commonly as an address to any woman since 1890s.
Applied since Old English to the Holy Virgin, hence many extended usages in plant names, place names, etc., from genitive singular hlæfdigan, which in Middle English merged with the nominative, so that lady- often represents (Our) Lady's, as in ladybug. Lady Day (late 13c.) was the festival of the Annunciation of the Virgin Mary (March 25). Ladies' man first recorded 1784; lady-killer "man supposed to be dangerously fascinating to women" is from 1811. Lady of pleasure recorded from 1640s. Lady's slipper as a type of orchid is from 1590s.
1707 as a direct phrase, but implied much earlier, and Old Norse had bikkju-sonr. Abbreviated form SOB from 1918; form sumbitch attested in writing by 1969.
Abide þou þef malicious!
Biche-sone þou drawest amis
þou schalt abigge it ywis!
["Of Arthour & of Merlin," c. 1330]
"Probably the most common American vulgarity from about the middle of the eighteenth century to the middle of the twentieth" [Rawson].
Our maid-of-all-work in that department [indecency] is son-of-a-bitch, which seems as pale and ineffectual to a Slav or a Latin as fudge does to us. There is simply no lift in it, no shock, no sis-boom-ah. The dumbest policeman in Palermo thinks of a dozen better ones between breakfast and the noon whistle. [H.L. Mencken, "The American Language," 4th ed., 1936, p.317-8]
Elsewhere, complaining of the tepidity of the American vocabulary of profanity, Mencken writes that the toned-down form son-of-a-gun "is so lacking in punch that the Italians among us have borrowed it as a satirical name for an American: la sanemagogna is what they call him, and by it they indicate their contempt for his backwardness in the art that is one of their great glories."
It was in 1934 also that the New York Daily News, with commendable frankness, in reporting a hearing in Washington at which Senator Huey P. Long featured, forsook the old-time dashes and abbreviations and printed the complete epithet "son of a bitch." [Stanley Walker, "City Editor," 1934]
c. 1300, "determined, fixed," from Old French certain "reliable, sure, assured" (12c.), from Vulgar Latin *certanus, extended form of Latin certus "determined, resolved, fixed, settled," of things whose qualities are invariable, "established," also "placed beyond doubt, sure, true, proved; unerring, to be depended upon" (also source of Old French cert, Italian certo, Spanish cierto), originally a variant past participle of cernere "to distinguish, decide," literally "to sift, separate." This Latin verb comes from the PIE root *krei- "to sieve," thus "discriminate, distinguish," which is also the source of Greek krisis "turning point, judgment, result of a trial" (compare crisis).
Transferred sense, in reference to persons, "full of confidence in one's knowledge or judgment, made certain in reference to a matter or thing," from mid-14c. (also a sense in Latin). Meaning "established as true beyond doubt" in English is from c. 1400. Meaning "indefinite, not specifically named, known but not described" is from late 14c.
Different as this seems to be from sense I, it is hardly separable from it in a large number of examples: thus, in [a certain hour], the hour was quite 'certain' or 'fixed', but it is not communicated to the reader; to him it remains, so far as his knowledge is concerned, quite indefinite; it may have been, as far as he knows, at any hour; though, as a fact, it was at a particular hour. [OED]
Lewis & Short write that Latin certus also was sometimes indefinite, "of things, the certainty of whose existence is given, but whose nature is not more definitely designated, or comes not into consideration ...."
Hence the euphemistic use, attested from mid-18c., as in woman of a certain age "an old maid;" woman of a certain description "disreputable woman;" in a certain condition "pregnant;" a certain disease "venereal disease;" of a certain weight "obese." Used with proper names from 1785, "often conveying a slight shade of disdain" [OED]. Certainer, certainest were common to c. 1750, but have fallen from proper use for some reason. Expression for certain "assuredly" is attested by early 14c.
c. 1400, "a dirty, slovenly, or untidy woman," according to OED "Of doubtful origin," but probably cognate with dialectal German Schlutt "slovenly woman," dialectal Swedish slata "idle woman, slut," and Dutch slodde "slut," slodder "a careless man," but the exact relationship of all these is obscure. Chaucer uses sluttish (late 14c.) in reference to the appearance of an untidy man. Also "a kitchen maid, a drudge" (mid-15c.; hard pieces in a bread loaf from imperfect kneading were called slut's pennies, 18c.).
Specific modern sense of "woman who enjoys sex in a degree considered shamefully excessive" is by 1966. Meaning "woman of loose character, bold hussy" is attested from mid-15c., but the primary association through 18c. was untidiness. Johnson has it (second definition) as "A word of slight contempt to a woman" but sexual activity does not seem to figure into his examples. Playful use of the word, without implication of messiness or loose morals, is attested by 1660s:
My wife called up the people to washing by four o'clock in the morning; and our little girl Susan is a most admirable slut, and pleases us mightily, doing more service than both the others, and deserves wages better. [Pepys, diary, Feb. 21, 1664]
Compare playful use of scamp, etc., for boys. Sometimes used 19c. as a euphemism for bitch to describe a female dog.
There is a group of North Sea Germanic words in sl- that mean "sloppy," and also "slovenly woman" and, less often, "slovenly man," and that tend to evolve toward "woman of loose morals." Compare slattern, also English dialectal slummock "a dirty, untidy, or slovenly person" (1861), variant of slammacks "slatternly woman," said to be from slam "ill-shaped, shambling fellow." Also slammakin (from 1756 as a type of loose gown; 1785 as "slovenly female," 1727 as a character name in Gay's "Beggar's Opera"), with variants slamkin, slammerkin. Also possibly related are Middle Dutch slore "a sluttish woman," Dutch slomp, German schlampe "a slattern."
"artificial penis used for female gratification," 1590s, a word of unknown origin. Traditional guesses include a corruption of Italian deletto "delight" (from Latin dilectio, noun of action from diligere "to esteem highly, to love;" see diligence) or a corruption of English diddle. None of these seems very convincing (Florio's dictionary glosses many words with dildo, but diletto is not one of them.) Century Dictionary perhaps gets closer to the mark:
A term of obscure cant or slang origin, used in old ballads and plays as a mere refrain or nonsense-word; also used, from its vagueness, as a substitute for various obscene terms and in various obscene meanings. 
The earliest use of the word in this sense, and probably the start of its popularity, seems to be via Nashe:
"Curse Eunuke dilldo, senceless counterfet" ["Choise of Valentines or the Merie Ballad of Nash his Dildo," T. Nashe, c. 1593]
Other early forms include dildoides (1675), dildidoes (1607). Middle English had dillidoun (n.) "a darling, a pet" (mid-15c.), from Old Norse dilla "to lull" (hence dillindo "lullaby"). That sense probably survived into Elizabethan times, if it is the word in Jonson's "Cynthia's Revels":
Chorus: Good Mercury defend vs.
Phan.: From perfum'd Dogs, Monkeys, Sparrowes, Dildos, and Parachitos.
And dildin seems to be a term for "sweetheart" in a 1675 play:
Mir.: Here comes a lusty Wooer, my dildin, my darling.
Here comes a lusty Wooer Lady bright and shining.
The thing itself is older. A classical Latin word for one was fascinum (see fascinate). In later English sometimes a French word, godemiché, was used (1879). Also used in 18c. of things that resemble dildoes, e.g. dildo pear (1756), dildo cactus (1792).
Shakespeare plays on the double sense, sexual toy and ballad refrain, in "A Winter's Tale."
SERVANT: He hath songs for man or woman, of all sizes; no
milliner can so fit his customers with gloves: he
has the prettiest love-songs for maids; so without
bawdry, which is strange; with such delicate
burthens of dildos and fadings, 'jump her and thump
her;' and where some stretch-mouthed rascal would,
as it were, mean mischief and break a foul gap into
the matter, he makes the maid to answer 'Whoop, do me
no harm, good man;' puts him off, slights him, with
'Whoop, do me no harm, good man.'
early 15c., "servants of a household," from Latin familia "family servants, domestics collectively, the servants in a household," thus also "members of a household, the estate, property; the household, including relatives and servants," abstract noun formed from famulus "servant, slave," which is of unknown origin.
The Latin word rarely appears in the sense "parents with their children," for which domus (see domestic (adj.)) was used. Derivatives of famulus include famula "serving woman, maid," famulanter "in the manner of a servant," famulitas "servitude," familiaris "of one's household, private," familiaricus "of household slaves," familiaritas "close friendship."
In English, sense of "collective body of persons who form one household under one head and one domestic government, including parents, children, and servants, and as sometimes used even lodgers or boarders" [Century Dictionary] is from 1540s. From 1660s as "parents with their children, whether they dwell together or not," also in a more general sense, "persons closely related by blood, including aunts, uncles, cousins;" earlier "those who descend from a common progenitor, a house, a lineage" (1580s). Hence, "any group of things classed as kindred based on common distinguishing characteristics" (1620s); as a scientific classification, between genus and order, from 1753.
Latin familia often was glossed in Old English by hired, hyred "household, family, retinue" (for which see hide (n.2), and also by hiwscipe, hiwræden, hiwan "members of a family, household, or religious house," which is cognate with Old Norse hjon "one of the household; married couple, man and wife; domestic servant," and with Old High German hiwo "husband," hiwa "wife," also with Lithuanian šeimyna "family," Gothic haims "village," Old English ham "village, home" (see home (n.)). A 15c. glossary has, for Latin familia, Middle English a menge, from Anglo-French maisnie "the household, the whole attendance upon the personal establishment of the feudal lord."
As an adjective from c. 1600; with the meaning "suitable for a family," by 1807. Family values is recorded by 1966. Phrase in a family way "pregnant" is from 1796. Family circle is 1809; family man "man devoted to wife and children, man inclined to lead a domestic life" is 1856 (earlier it meant "thief," 1788, from family in a slang sense of "the fraternity of thieves"). Family tree "graph of ancestral relations" attested from 1752.
He was dressed in his best Coat, which had served him in the same Capacity before my Birth, and possibly, might be but little short in Antiquity, to the Root of his third Family Tree; and indeed, he made a venerable Figure in it. ["A Genuine Account of the Life and Transactions of Howell ap David Price, Gentleman of Wales," London, 1752]