落とし穴

Etymology
Compound of. Originally referred to a kind of trap.

First attested to the early 1200s.

Noun

 * 1)  a pit trap or snare
 * 2)  a hole in the top of a box or other container for dropping things in
 * 3)   a deliberate ploy to deceive someone into a bad situation: a deliberate pitfall
 * 4)   an unknown pitfall, a non-deliberate hidden risk
 * 1)   an unknown pitfall, a non-deliberate hidden risk
 * 1)   an unknown pitfall, a non-deliberate hidden risk