Old English freo "exempt from; not in bondage, acting of one's own will," also "noble; joyful," from Proto-Germanic *friaz "beloved; not in bondage" (source also of Old Frisian fri, Old Saxon vri, Old High German vri, German frei, Dutch vrij, Gothic freis "free"), from PIE *priy-a- "dear, beloved," from root *pri- "to love."
The sense evolution from "to love" to "free" is perhaps from the terms "beloved" or "friend" being applied to the free members of one's clan (as opposed to slaves; compare Latin liberi, meaning both "free persons" and "children of a family"). For the older sense in Germanic, compare Gothic frijon "to love;" Old English freod "affection, friendship, peace," friga "love," friðu "peace;" Old Norse friðr "peace, personal security; love, friendship," German Friede "peace;" Old English freo "wife;" Old Norse Frigg, name of the wife of Odin, literally "beloved" or "loving;" Middle Low German vrien "to take to wife," Dutch vrijen, German freien "to woo."
Meaning "clear of obstruction" is from mid-13c.; sense of "unrestrained in movement" is from c. 1300; of animals, "loose, at liberty, wild," late 14c. Meaning "liberal, not parsimonious" is from c. 1300. Sense of "characterized by liberty of action or expression" is from 1630s; of art, etc., "not holding strictly to rule or form," from 1813. Of nations, "not subject to foreign rule or to despotism," recorded in English from late 14c. (Free world "non-communist nations" attested from 1950 on notion of "based on principles of civil liberty.") Sense of "given without cost" is 1580s, from notion of "free of cost."
Free even to the definition of freedom, "without any hindrance that does not arise out of his own constitution." [Emerson, "The American Scholar," 1837]
Free lunch, originally offered in bars to draw in customers, by 1850, American English. Free pass on railways, etc., attested by 1850. Free speech in Britain was used of a privilege in Parliament since the time of Henry VIII. In U.S., in reference to a civil right to expression, it became a prominent phrase in the debates over the Gag Rule (1836). Free enterprise recorded from 1832; free trade is from 1823; free market from 1630s. Free will is from early 13c. Free school is from late 15c. Free association in psychology is from 1899. Free love "sexual liberation" attested from 1822 (the doctrine itself is much older), American English. Free and easy "unrestrained" is from 1690s.
1756, "special vocabulary of tramps or thieves," later "jargon of a particular profession" (1801). The sense of "very informal language characterized by vividness and novelty" is by 1818.
Anatoly Liberman writes here an extensive account of the established origin of the word from the Northern England noun slang "a narrow piece of land running up between other and larger divisions of ground" and the verb slanger "linger, go slowly," which is of Scandinavian origin (compare Norwegian slenge "hang loose, sling, sway, dangle," Danish slænge "to throw, sling"). "Their common denominator seems to be 'to move freely in any direction' " [Liberman]. Noun derivatives of these (Danish slænget, Norwegian slenget) mean "a gang, a band," and Liberman compares Old Norse slangi "tramp" and slangr "going astray" (used of sheep). He writes:
It is not uncommon to associate the place designated for a certain group and those who live there with that group’s language. John Fielding and the early writers who knew the noun slang used the phrase slang patter, as though that patter were a kind of talk belonging to some territory.
So the sense evolution would be from slang "a piece of delimited territory" to "the territory used by tramps for their wandering," to "their camping ground," and finally to "the language used there." The sense shift then passes through itinerant merchants:
Hawkers use a special vocabulary and a special intonation when advertising their wares (think of modern auctioneers), and many disparaging, derisive names characterize their speech; charlatan and quack are among them.
[Slang] is a dialectal word that reached London from the north and for a long time retained the traces of its low origin. The route was from "territory; turf" to "those who advertise and sell their wares on such a territory," to "the patter used in advertising the wares," and to "vulgar language" (later to “any colorful, informal way of expression”).
[S]lang is a conscious offence against some conventional standard of propriety. A mere vulgarism is not slang, except when it is purposely adopted, and acquires an artificial currency, among some class of persons to whom it is not native. The other distinctive feature of slang is that it is neither part of the ordinary language, nor an attempt to supply its deficiencies. The slang word is a deliberate substitute for a word of the vernacular, just as the characters of a cipher are substitutes for the letters of the alphabet, or as a nickname is a substitute for a personal name. [Henry Bradley, from "Slang," in Encyclopedia Britannica, 11th ed.]
A word that ought to have survived is slangwhanger (1807, American English) "noisy or abusive talker or writer."
also God; Old English god "supreme being, deity; the Christian God; image of a god; godlike person," from Proto-Germanic *guthan (source also of Old Saxon, Old Frisian, Dutch god, Old High German got, German Gott, Old Norse guð, Gothic guþ), which is of uncertain origin; perhaps from PIE *ghut- "that which is invoked" (source also of Old Church Slavonic zovo "to call," Sanskrit huta- "invoked," an epithet of Indra), from root *gheu(e)- "to call, invoke." The notion could be "divine entity summoned to a sacrifice."
But some trace it to PIE *ghu-to- "poured," from root *gheu- "to pour, pour a libation" (source of Greek khein "to pour," also in the phrase khute gaia "poured earth," referring to a burial mound; see found (v.2)). "Given the Greek facts, the Germanic form may have referred in the first instance to the spirit immanent in a burial mound" [Watkins]. See also Zeus. In either case, not related to good.
Popular etymology has long derived God from good; but a comparison of the forms ... shows this to be an error. Moreover, the notion of goodness is not conspicuous in the heathen conception of deity, and in good itself the ethical sense is comparatively late. [Century Dictionary, 1897]
Originally a neuter noun in Germanic, the gender shifted to masculine after the coming of Christianity. Old English god probably was closer in sense to Latin numen. A better word to translate deus might have been Proto-Germanic *ansuz, but this was used only of the highest deities in the Germanic religion, and not of foreign gods, and it was never used of the Christian God. It survives in English mainly in the personal names beginning in Os-.
I want my lawyer, my tailor, my servants, even my wife to believe in God, because it means that I shall be cheated and robbed and cuckolded less often. ... If God did not exist, it would be necessary to invent him. [Voltaire]
God bless you after someone sneezes is credited to St. Gregory the Great, but the pagan Romans (Absit omen) and Greeks had similar customs. God's gift to _____ is by 1931. God of the gaps means "God considered solely as an explanation for anything not otherwise explained by science;" the exact phrase is from 1949, but the words and the idea have been around since 1894. God-forbids was rhyming slang for kids ("children"). God squad "evangelical organization" is 1969 U.S. student slang. God's acre "burial ground" imitates or partially translates German Gottesacker, where the second element means "field;" the phrase dates to 1610s in English but was noted as a Germanism as late as Longfellow.
How poore, how narrow, how impious a measure of God, is this, that he must doe, as thou wouldest doe, if thou wert God. [John Donne, sermon preached in St. Paul's Jan. 30, 1624/5]