butyoudaoicibaDictgodict[but 词源字典]
but: [OE] But originally meant ‘outside’. It was a compound word formed in prehistoric West Germanic from *be (source of English by) and *ūtana (related to English out). This gave Old English būtan, which quickly developed in meaning from ‘outside’ to ‘without, except’, as in ‘all but me’ (the sense ‘outside’ survived longer in Scotland than elsewhere). The modern conjunctive use of but did not develop until the late 13th century.
=> by, out[but etymology, but origin, 英语词源]
but (adv., prep.)youdaoicibaDictgodict
Old English butan, buton "unless, except; without, outside," from West Germanic *be-utan, a compound of *be- "by" (see by) + *utana "out, outside; from without," from ut "out" (see out (adv.)). Not used as a conjunction in Old English. As a noun from late 14c.