UsageA widely used Mexican idiom meaning "to finally understand or realize something" — the mental click of comprehension, like the English "the penny drops." Rooted in old pay phones that required a 20-centavo coin to physically drop into the mechanism before the call would connect.
Examples- Le tomó un rato, pero por fin le cayó el veinte. — It took him a while, but the penny finally dropped.
- Cuando vio la foto, me cayó el veinte de quién era. — When I saw the photo, it clicked who it was.
- A ver si te cae el veinte antes del examen. — Let's hope it clicks for you before the exam.
Common mistakeThis idiom is specifically Mexican and would puzzle speakers from most other countries — darse cuenta (to realize) is the neutral, universally understood alternative.
In real life- expression Origen telefónico de "caer el veinte" — The expression traces back to Mexico's old coin-operated public telephones, which required a 20-centavo coin to physically drop into the internal mechanism before a call would connect — the phrase later became a fixture of everyday Mexican Spanish for the moment understanding "clicks."