Sh (quiet!)

The sound 'sh' (IPA [ʃ]) occurs as an interjection, meaning "quiet!", in many languages, including English, Hebrew , Polish.

In Hebrew, it happens to be the first sound of the word 'sheket' meaning 'quiet!'.

The Swedish linguist and comedian Fredrik Lindström claims, in his book Jordens smartaste ord (The world's smartest word), that the interjection is found with the same meaning in nearly all of the world's languages.