Buddy
mid 19th century (originally US): perhaps an alteration of brother, or a variant of butty2.
wiktionary
1802, 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. [1] Alternatively, an alteration of brother. [2] [3]
From Middle English buddy, buddi, equivalent to bud + -y.
etymonline
buddy (n.)
1850, American English, possibly an alteration of brother, or from British colloquial butty "companion" (1802), itself perhaps a variant of booty in booty fellow "confederate who shares plunder" (1520s). But butty, meaning "work-mate," also was a localized dialect word in England and Wales, attested since 18c., and long associated with coal miners. Short form bud is attested from 1851. Reduplicated form buddy-buddy (adj.) attested by 1952, American English.
Lenny Kent, a long-time fave here, is really in his element. ... After four weeks here he's got everyone in town saying, "Hiya, Buddy, Buddy" with a drawl simulating his. [Review of Ned Schuyler's 5 O'Clock Club, Miami Beach, Fla., Billboard, Nov. 12, 1949]
Buddy system attested from 1920.
buddy (v.)
1925, usually with up, from buddy (n.); perhaps originally U.S. underworld slang. Related: Buddied; buddying.
