No decir ni mu
Not to say even "moo".
not to say a word; **not to say a word**; **not to say a thing**; **to keep quiet**; **to remain silent**; **to keep one's mouth shut**; **not to utter a word**
No decir ni mu means not to say a word, to remain completely silent, or not to say anything at all.
Le preguntamos qué había pasado, pero no dijo ni mu.
We asked him what had happened, but he didn't say a word.
No digas ni mu de esto, ¿eh?
Don't say a word about this, okay?
Estuvo toda la reunión sin decir ni mu.
He remained completely silent throughout the meeting.
Se lo contaron todo y él no dijo ni mu.
They told him everything and he didn't say a thing.
No ha dicho ni mu sobre el asunto.
He hasn't said a word about it.
It is usually used to emphasise that someone kept completely quiet, especially when they were expected or invited to speak.
A common construction is:
No dijo ni mu.
→ He didn't say a word.
- remains completely silent
- refuses to answer
- says nothing about a particular matter
- keeps a secret
- does not complain or protest
- avoids revealing information
The expression uses mu, the traditional Spanish representation of the sound made by a cow.
The choice is humorous: even a cow's minimal contribution to a conversation is reduced to "mu", so someone who doesn't say ni mu does not utter even the tiniest sound.
The expression belongs to a broader Spanish pattern in which a very small or insignificant thing is used after ni to mean "not even the slightest amount".
The expression can mean either deliberate silence or simply complete lack of speech.
Compare:
No habló durante la reunión.
→ He didn't speak during the meeting.
with:
No dijo ni mu durante la reunión.
→ He didn't say a word during the meeting.
The second is more expressive and often suggests that his silence was noticeable or significant.
It can also be an instruction:
¡No digas ni mu!
→ Don't say a word!
Spanish has several humorous expressions meaning "not to say a word":
- No decir ni mu → not say a word.
- No decir ni pío → not say a peep.
- No decir ni esta boca es mía → not utter a word.
- No soltar prenda → not give anything away.
The use of animal sounds is especially striking:
ni mu → not even "moo"
while:
ni pío → not even "tweet"/"peep".
Both use a tiny sound to express absolute silence.
Do not translate:
No dijo ni mu.
as:
He didn't say moo.
unless you are deliberately making a joke about the literal wording.
Natural translations include:
He didn't say a word.
He didn't utter a word.
He kept completely quiet.
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