buddy

First appears c. 1788, in the writings of Charles Dibdin, of uncertain origin. Possibly from *bruddy, *bruthy, a child-talk alteration of brother. Alternatively, perhaps from British colloquial butty (“companion”), also the form of an older dialect term meaning workmate, associated with coal mining. Itself believed derived from 1530 as booty fellow, a partner with whom one shares booty or loot. Alternatively, compare Scots buddo, bodda (“buddy, kiddo, dear”), related to Icelandic budda (“purse"; also "short, stout person”).

出典: Wiktionary「buddy」（CC BY-SA 4.0）