No tener pelos en la lengua

Literally: To have no hairs on the tongue

Example: “La doctora no tiene pelos en la lengua: me dijo que debía dejar de fumar ya.” — The doctor didn't mince her words: she told me to quit smoking immediately.

English equivalent: Not to mince one's words

Origin: The tongue has long stood as a symbol of cultivated, careful speech, and the image of hairs growing on it works as an imagined physical obstacle — something that would genuinely get in the way of speaking cleanly and freely. "Not having" that obstacle came to mean speaking without any hesitation or self-censorship, however blunt or uncomfortable the result. The exact date of the phrase's coinage isn't documented, though it's generally associated with the Spanish Golden Age of the 16th and 17th centuries, a period when Spanish idiom and proverb collections were being actively compiled and written down for the first time.