Emily Dickinson Lexicon

BUT, prep. [Sax. butan, buton, buta, bute, without, on the outside, abroad: hence, except or excepting, besides; that is, separated, not included. The verb is not in the Saxon; but in Dutch we have the verb in its primary sense, buiten, to rove or wander, to go freebooting; buit, booty; buiten, out, without, abroad, besides, except; buiten boord, over board; buiten deur, out of doors; buiten huis, an outhouse; buiten man, an out-man, a stranger; G. beute, booty; Sw. byte, booty; byta, to exchange; Dan. bytte, booty, a parting, division, distribution; bytter, to part, divide, exchange, barter; Sp. botin; It. bottino; Fr. butin, booty. The primary sense of booty is to rove or wander, to part or separate from; applied to persons, it is to wander; applied to things, it may include stripping. But then is a contraction of butan, and primarily a participle.]

1. Except; besides; unless. Who can it be, but perjured Lycon? – Smith. That is, removed, separated, excepted. Lycon being separated, or excepted, who can it be? And but infirmity, / Which waits upon worn times, hath something seized / His wished ability, he had himself / The lands and waters measured. – Shak. That is, except, unless, separate this fact, that infirmity had seized his ability, he had measured the lands and waters. In this use but, butan, is a participle equivalent to excepting, and may be referred to the person speaking, or more naturally, it is equivalent to excepted, and with the following words, or clause, forming the case absolute. Who can it be, Lycon being excepted? And but my noble Moor is true of mind, it were enough to put him to ill thinking. – Shak. It cannot be but nature hath some director, of infinite power, to guide her in all her ways. – Hooker. There is no question but the King of Spain will reform most of the abuses. – Addison. It is not impossible but I may alter the complexion of my play. – Dryden. In the last three examples, that is omitted after but. It is not impossible but that I may alter the complexion of my play. In these and all similar phrases but denotes separation, exception.
2. Only; as, there is but one man present. A formidable man, but to his friends. – Dryden. This use of but is a modern innovation; but perhaps too firmly established to be corrected. In all such phrases, a negative, not, nothing, or other word, is omitted. He is not a formidable man, but to his enemies, that is, except. There is not but one man present, that is, there is not except or besides one present. So also, “Our light affliction is but for a moment.” – 2 Cor. iv. Our affliction is not, except for a moment. If they kill us, we shall but die. – 2 Kings vii. The common people in America retain the original and correct phrase; usually employing a negative. They do not say, I have but one. On the other hand, they say, I have not but one, that is, I have not except one; except one, and I have none. This word but for butan is not a conjunction, nor has it the least affinity to that part of speech.