Dear Word Detective: I am wondering how the phrase “for good” came to mean “forever,” as in “He finally quit smoking for good.” There may be some interesting philosophical roots to this idiom. — Josiah Kollmeyer.
Perhaps. But probably not. Generally speaking, the English language is random, resistant to logic, and contemptuous of continuity to a degree that seems almost willfully perverse. Sometimes, in fact, the whole shebang makes a million monkeys with typewriters look like a good plan for imposing some coherence, provided we can wean them from writing scripts for HBO. Don’t mind me; I get this way in election years. But have you noticed that almost every prime time TV show in the US at the moment involves super psychic cops and serial killers? This does not seem like the harbinger of a new Age of Aquarius, to put it mildly.
Meanwhile, back at your question, that’s a darn good one, using “good” in one of its common adjectival senses of “sound, cogent, fit, suitable, appropriate.” The adjective and adverb forms of “good” have a whole herd of other meanings too, most of which connote a positive sense of the thing or action that they describe. There is also, of course, the noun “good,” which can mean anything from the abstract sense of “something positive” to “something produced for sale” (usually in the plural “goods”). “Good,” in other words, comes with a lot of wiggle room, which is “good” because it makes “good” a very useful word. But it also sometimes makes “good” a mysterious and maddeningly vague one.
“Good” first appeared in Old English as “god” (with a long “o,” meaning that it sounded like “goad”). The source of our “good,” and similar forms in German, Swedish, etc., was the Proto-Germanic root “godo,” which may be a variant of the root “gad,” meaning “to bring together, to unite,” also giving us the English verb “gather.” The earliest sense of our adjective “good” was simply “suitable, fitting, appropriate.” Our “good” lacks the expected comparative and superlative forms (which would be “gooder” and “goodest”); instead we use “better” and “best.” The adverb in English corresponding to our adjective “good” is, of course, “well.”
Most of the senses developed by “good” over the centuries have carried a connotation of the thing, action, person, etc., being satisfactory, appropriate or sufficient. What’s “good” is good, not wonderful or fantastic, but solidly OK. That sense of “sufficient” has given us the use of “good” in “good for,” with either a task or a time appended, as in “These batteries are good for twelve hours” or “That mower is only good for small lawns.” We also use “good” to mean “a considerable amount” (“It’s a good ways to the next gas station”) and to mean “at least” (“He walked a good ten miles every day”). This sense of “substantial” also underlies the intensifying phrase “good and” (“Bob was good and drunk after his eighth beer”).
It’s this sense of “completeness” that gives us the phrase “for good” meaning “finally” or “forever.” When something is settled “for good,” the result may not be “good” in the sense of “positive or desirable,” but it’s definitely over (“After Lyle’s third arrest for mopery, Karen moved out for good”). The original form of the phrase, when it first appeared in the early 16th century, was, in fact, “for good and all,” which is an even more emphatic way to say “it’s over” (“He was obliged for good and all to leave his country,” Thomas Boston, circa 1732).