cloak-and-dagger
adjective
Synonyms
covert clandestine undercover abstruse behind the scenes catlike backroom backstairs stealth concealed confidential deep-laid dern disguised furtive huggermugger hush-hush inconspicuous incognito low profile hole-and-corner hugger-mugger secret surreptitious underground
Etymology
Calque of French de cape et d'épée (“of the cloak and the sword”); first attested 1840. The French term referred to a genre of drama in which the main characters wore cloaks and had swords. Henry Wadsworth Longfellow used the “cloak and sword” term in 1840, whereas Charles Dickens preferred “cloak and dagger” a year later.
Sources: Wiktionary · WordNet 3.0 — from the Wiktionary entry “cloak-and-dagger”, CC BY-SA 4.0. Details