The underside or bottom part of an animal; used figuratively to mean the hidden or shameful aspects of something.
Compound word from 'under' and 'belly,' appearing in English by the 18th century in literal usage. The figurative sense developed in the 20th century, especially in noir fiction and detective writing to describe the dark side of cities or organizations.
The underbelly became a literary metaphor during the noir period when writers needed language for the corruption hidden beneath society's respectable surface. Physically, an animal's underbelly is its most vulnerable, defenseless part—so the metaphor cleverly suggests that society's illegal side is both hidden and fragile.
Complete word intelligence in one call. Free tier — 50 lookups/day.