underside
UK: ˈʌndəsaɪd | US: ˈʌndərˌsaɪd
n. the lower or bottom side of something
n. (figurative) a less visible or favorable aspect of a situation
The word "underside" is a straightforward compound formed by combining "under" (Old English under, meaning "beneath") and "side" (Old English sīde, meaning "flank" or "surface"). It emerged in Middle English (14th century) to literally describe the bottom surface of an object. Over time, it gained figurative use to denote hidden or negative aspects, reflecting the metaphorical association of "below" with obscurity or inferiority.
The underside of the leaf was covered in tiny hairs.
He flipped the rug to inspect its underside for stains.
The documentary exposed the dark underside of the fashion industry.
Always check the underside of your car for leaks.
Her cheerful demeanor hid an underside of deep insecurity.