Hush-hush and On the QT

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

On the QT and hush-hush are semantically related In some cases you can use "On the QT" instead the phrase "Hush-hush" as an adverb or an adjective.

On the QT adverb - In secrecy; not openly.

Hush-hush and on the QT are semantically related in confidential topic. You can use "Hush-hush" instead the phrase "On the QT" as an adverb or an adjective, if it concerns topics such as secret, shy, sneaky, deceitful.