A close friend or companion; alternatively, a British term for buttocks (informal/childish).
Possibly from 'bum' combined with diminutive suffix '-ie', or from Cockney rhyming slang. Used in both British and Australian English with different emphases.
This word shows how the same term can mean totally different things in different English dialects—Australian for friend, British for something you sit on—a perfect example of how English fractures across the globe.
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