Hush-hush and Tongue-tie

Hush-hush adjective - Not known or meant to be known by the general populace.

Tongue-tie and hush-hush are semantically related In some cases you can use "Tongue-tie" instead a verb phrase "Hush-hush".

Tongue-tie verb - Deprive of speech.

Hush-hush and tongue-tie are semantically related in silence topic. You can use "Hush-hush" instead a verb phrase "Tongue-tie", if it concerns topics such as make or be quiet.