Q Where did we get the word “wig” for a fake head of hair? – H.C., Cumberland, Md.

A: In the early 16th century, it was fashionable for women, and later for men, to wear a headpiece of artificial hair called a “periwig.” “Periwig” developed from the earlier “perwyke,” a modification of the Middle French “perruque,” from Old Italian “perruea,” meaning “head of hair.”

“Periwig” became simply “wig” through what etymologists call “clipping” or “truncation.” These terms denote primarily the process whereby an appreciable chunk of a 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” is docked to give “exam.” Less common in English are “fore-clippings,” in which the beginning of a word is dropped, as with “wig.” Very occasionally we see a sort of fore-and-aft clipping, as when “flu” was derived from “influenza.”

Clipping is an ongoing process in the history of English. Its products tend to have a probational status at first – as when Jonathan Swift denounced “mob” when that word was newly clipped from Latin “mobile-vulgus” (“fickle populace”) – but may in time be absorbed wholly into the language. We may distinguish several stages in the process.

The most solid state of acceptance of a clipped form comes when many speakers no longer even know what the earlier and longer form of the word was. Thus “chap,” meaning “fellow,” no longer evokes its antecedant “chapman,” an old term for a merchant. A “hack,” meaning a cab, has for most speakers cut its historical ties with “hackney,” which originally designated a kind of horse. Similar remarks apply to “pants” ( from “pantaloons”), “cinema” (from “cinematograph”), and many others. Status as a completely independent word is further enhanced when the phonetic substance of the word is also altered, as when “perambulator” (“baby carriage”) yielded “pram,” not “peram,” and “geneva” gave rise to “gin.”

The status of a clipping is more provisional when speakers can in general tell you right off what word it was clipped from. “Exam,” “gym,” “lab,” “ad,” and “mike” are all very familiar words and must be considered part of the standard language, but anyone who knows the words at all can probably tell you where they come from, and the very availability of a recognizable longer source word makes their shorter offspring seem somewhat more informal. Just how breezily curtailed a word feels varies in ways not altogether predictable: somehow “math” sounds more formal than “chem” for “chemistry” or “sosh” for “sociology.”

Finally, there are clippings that are frankly slangy and not, or not yet, seriously applying for citizenship in the standard lexicon. Such are “vac” for “vacation” and “caf” for “cafeteria.”

This column was prepared by the editors of Merriam-Webster’s Collegiate Dictionary, Tenth Edition. Readers may send questions to Merriam-Webster’s Wordwatch, P.O. Box 281, 47 Federal St., Springfield, Mass. 01102.