A boxer or wrestler in the heaviest weight class, or a person of great influence or importance in a particular area.
Compound of 'heavy' + 'weight', originally from boxing terminology in the late 19th century. The metaphorical sense of 'important person' developed from the prestige associated with heavyweight boxing champions.
Boxing weight classes gave us a whole vocabulary for describing importance and influence. Calling someone a 'heavyweight' in business or politics draws on our cultural understanding that the biggest fighters are often the most prestigious and powerful.
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