It is a popular saying whose meaning is that the person who keeps silent and does not express his opinion, agrees and gives (grants) consent or agree to what has been said or done as valid.Example.Question: are we going to the movies?Answer: (it says nothing. Stays silent)Conclusion: the calla grants (is van to the cinema).
Castilian, not always true, saying that has its origin in the Canon law, in particular in the sixth book, which added Bonifacio VIII in the 13th century to the five books of the decretals of Gregory IX. In latin, qui tacet, consentire videtur; subsequently be pointed out: qui tacet, ubi loqui debuit, consentire videtur et potuit: who is silent, when he could and he should speak, seems that it grants. Therefore, which is silent when it is accused of something and not upheld and can and must do so, seems to be guilty.