Where do new words come from? How do you figure out their histories?
An etymology is the history of a linguistic form, such as a word; the same term is also used for the study of word histories. A dictionary etymology tells us what is known of an English word before it became the word entered in that dictionary. If the word was created in English, the etymology shows, to whatever extent is not already obvious from the shape of the word, what materials were used to form it. If the word was borrowed into English, the etymology traces the borrowing process backward from the point at which the word entered English to the earliest records of the ancestral language. Where it is relevant, an etymology notes words from other languages that are related ("akin") to the word in the dictionary entry, but that are not in the direct line of borrowing.
An etymologist, a specialist in the study of etymology, must know a good deal about the history of English and also about the relationships of sound and meaning and their changes over time that underline the reconstruction of the Indo-European language family. Knowledge is also needed of the various processes by which words are created within Modern English; the most important processes are listed below.
A majority of the words used in English today are of foreign origin. English still derives much of its vocabulary from Latin and Greek, but we have also borrowed words from nearly all of the languages in Europe. In the modern period of linguistic acquisitiveness, English has found vocabulary opportunities even farther afield. From the period of the Renaissance voyages through the days when the sun never set upon the British Empire and up to the present, a steady stream of new words has flowed into the language to match the new objects and experiences English speakers have encountered all over the globe. Over 120 languages are on record as sources of present-day English vocabulary.
Clipping (or truncation) is a process whereby an appreciable chunk of an existing word is omitted, leaving what is sometimes called a stump word. When it is the end of a word that is lopped off, the process is called back-clipping: thus examination was docked to create exam and gymnasium was shortened to form gym. Less common in English are fore-clippings, in which the beginning of a word is dropped: thus phone from telephone. Very occasionally, we see a sort of fore-and-aft clipping, such as flu, from influenza.
A functional shift is the process by which an existing word or form comes to be used with another grammatical function (often a different part of speech); an example of a functional shift would be the development of the noun commute from the verb commute.
Back-formation occurs when a real or supposed affix (that is, a prefix or suffix) is removed from a word to create a new one. For example, the original name for a type of fruit was cherise, but some thought that word sounded plural, so they began to use what they believed to be a singular form, cherry, and a new word was born. The creation of the the verb enthuse from the noun enthusiasm is also an example of a back-formation.
A blend is a word made by combining other words or parts of words in such a way that they overlap (as motel from motor plus hotel) or one is infixed into the other (as chortle from snort plus chuckle the -ort- of the first being surrounded by the ch-...-le of the second). The term blend is also sometimes used to describe words like brunch, from breakfast plus lunch, in which pieces of the word are joined but there is no actual overlap. The essential feature of a blend in either case is that there be no point at which you can break the word with everything to the left of the breaking being a morpheme (a separately meaningful, conventionally combinable element) and everything to the right being a morpheme, and with the meaning of the blend-word being a function of the meaning of these morphemes. Thus, birdcage and psychohistory are not blends, but are instead compounds.
An acronym is a word formed from the initial letters of a phrase. Some acronymic terms still clearly show their alphabetic origins (consider FBI), but others are pronounced like words instead of as a succession of letter names: thus NASA and NATO are pronounced as two syllable words. If the form is written lowercase, there is no longer any formal clue that the word began life as an acronym: thus radar ('radio detecting and ranging'). Sometimes a form wavers between the two treatments: CAT scan pronounced either like cat or C-A-T.
NOTE: No origin is more pleasing to the general reader than an acronymic one. Although acronymic etymologies are perennially popular, many of them are based more in creative fancy than in fact. For an example of such an alleged acronymic etymology, see the article on posh.
Over time, names of people, places, or things may become generalized vocabulary words. Thus did forsythia develop from the name of botanist William Forsyth, silhouette from the name of Étienne de Silhouette, a parsimonious French controller general of finances, and denim from serge de Nîmes (a fabric made in Nîmes, France).
Words can also be created by onomatopoeia, the naming of things by a more or less exact reproduction of the sound associated with it. Words such as buzz, hiss, guffaw, whiz, and pop) are of imitative origin.
Folk etymology, also known as popular etymology, is the process whereby a word is altered so as to resemble at least partially a more familiar word or words. Sometimes the process seems intended to "make sense of" a borrowed foreign word using native resources: for example, the Late Latin febrigugia (a plant with medicinal properties, etymologically 'fever expeller') was modified into English as feverfew.
Also available to one who feels the need for a new word to name a new thing or express a new idea is the very considerable store of prefixes, suffixes, and combining forms that already exist in English. Some of these are native and others are borrowed from French, but the largest number have been taken directly from Latin or Greek, and they have been combined in may different ways often without any special regard for matching two elements from the same original language. The combination of these word elements has produced many scientific and technical terms of Modern English.
Once in a while, a word is created spontaneously out of the creative play of sheer imagination. Words such as boondoggle and googol are examples of such creative coinages, but most such inventive brand-new words do not gain sufficiently widespread use to gain dictionary entry unless their coiner is well known enough so his or her writings are read, quoted, and imitated. British author Lewis Carroll was renowned for coinages such as jabberwocky, galumph, and runcible, but most such new words are destined to pass in and out of existence with very little notice from most users of English.
An etymologist tracing the history of a dictionary entry must review the etymologies at existing main entries and prepare such etymologies as are required for the main entries being added to the new edition. In the course of the former activity, adjustments must sometimes be made either to incorporate a useful piece of information that has been previously overlooked or to review the account of the word's origin in light of new evidence. Such evidence may be unearthed by the etymologist or may be the product of published research by other scholars. In writing new etymologies, the etymologist must, of course, be alive to the possible languages from which a new term may have been created or borrowed, and must be prepared to research and analyze a wide range of documented evidence and published sources in tracing a word's history. The etymologist must sift theories, often-conflicting theories of greater or lesser likelihood, and try to evaluate the evidence conservatively but fairly to arrive at the soundest possible etymology that the available information permits.
When all attempts to provide a satisfactory etymology have failed, an etymologist may have to declare that a word's origin is unknown. The label "origin unknown" in an etymology seldom means that the etymologist is unaware of various speculations about the origin of a term, but instead usually means that no single theory conceived by the etymologist or proposed by others is well enough backed by evidence to include in a serious work of reference, even when qualified by "probably" or "perhaps."