q.t.

n. colloq. quiet (esp. on the q.t.).
Etymology: abbr.

* * *

/ˌkjuːˈtiː/

on the q.t. (or on the Q.T.)

informal : in a secret or quiet way

All the arrangements were made on the q.t.

She told me about it on the q.t.

This information is private, so keep it on the q.t. [=don't tell anyone about it]