The Spanish verb 'callar' (meaning 'to be silent') traces its origins back through Latin to Ancient Greek. It comes from the Latin verb 'callare' meaning 'to lower' or 'to be silent', which in turn was borrowed from the Ancient Greek 'khaláo' (χαλάω) meaning 'to loosen' or 'let down'. The semantic evolution from 'loosening/letting down' to 'being silent' likely developed from the idea of lowering one's voice or letting down the volume of speech.

A common related Spanish word is 'calla' (the imperative form of 'callar'), which is frequently used as a command meaning 'be quiet!' or 'shut up!'. The reflexive form 'callarse' is also commonly used to mean 'to keep quiet' or 'to shut oneself up'.

While English doesn't have any direct cognates from this Greek root, the concept of 'lowering' being connected to silence can be seen in English phrases like 'lower your voice' or 'keep it down', showing a similar semantic connection between downward movement and reducing sound.