A very recent and similar [question](https://english.stackexchange.com/q/40770/10041) was closed asks what "for good" means. While general reference can answer the question, I became curious as to the etymology of the idiom. [Googling](http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=%22for+good%22+%22etymology%22+forever) around got me nowhere, which is unusual. The closest I found was a thread in [wordorigins.org](http://www.wordorigins.org/index.php/forums/viewthread/119/):

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> **OED**  
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> **for good (and all)**: as a valid conclusion; hence, as a final act, finally. 
>  15.. *Parl. Byrdes Aij*, Than desyred al the Byrdes great and smal to mewe the hauke for good and all. **1603** in *Crt. & Times Jas. I* (1849) I. 25 D’Auval.. is gone for good and all. **1687** CONGREVE *Old Bach.* I. i, Ay, you may take him for good-and-all if you will. **1711** SWIFT *Jrnl.* to *Stella* 4 July, This day I left Chelsea for good, (that’s a genteel phrase). a **1732** T. BOSTON *Crook in Lot* (1805) 37 He was obliged for good and all to leave his country. **1850** J. H. NEWMAN *Diffic. Anglic.* 324 Throw off, for good and all, the illusions of your intellect. **1882** W. E. FORSTER *Let. To Gladstone* 10 Apr. in T. W. Reid *Life* (1888) II. viii. 421 This morning we released Parnell—not for good, but on parole.
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However, this only traces some historical usages, and suggests that *for good and all* used to be a more popular version of the current idiom. Is there anything more substantial? Why did "for good" come to mean "forever"?