Plural of heavy; people who are physically large and strong, or serious dramatic roles in acting, or the powerful members of an organization.
From Old English 'hefig' meaning having great weight; plural -s added; used colloquially since 1800s for powerful people or tough characters.
In theater, 'the heavies' refers to villain roles or dramatic characters—ironically, the most emotionally 'heavy' roles, not necessarily physically large characters.
Complete word intelligence in one call. Free tier — 50 lookups/day.