Hablar por los codos

Literally: To talk through the elbows

Example: “Mi tía habla por los codos; una llamada suya dura una hora.” — My aunt can talk your ear off; one of her calls lasts an hour.

English equivalent: To talk someone's ear off

Origin: Talking through one's elbows is talking so much that even one's elbows seem to join in. The phrase was in use by the 1830s, when Ramón de Mesonero Romanos wrote of a meeting where everyone hablaban por los codos at once. Two explanations are given, neither confirmed: the wild gesturing of great talkers, and the habit of nudging the listener with an elbow to hold their attention. Portuguese has the same phrase, falar pelos cotovelos.