Historical clue formulations

• Words that sometimes follow 1-Across — 2020-08-22
• "Keep this between us" ... or hint to this puzzle's circled letters — 2018-07-02
• What putting one's finger to one's lips may mean — 2017-08-03
• "Shhhh!" follower — 2011-05-28
• "Shhh!" — 2010-11-20
• "Mum's the word!" — 2009-06-15
• "Don't tell anyone!" — 2002-08-02