late 13c., "long, loose outer garment without sleeves," from Old North French cloque (Old French cloche, cloke) "traveling cloak," from Medieval Latin clocca "travelers' cape," literally "a bell," so called from the garment's bell-like shape (the word is thus a doublet of clock (n.1)).
An article of everyday wear for either sex in England through 16c. as a protection from the weather; a high-collared circular form revived as a fashion garment c. 1800-1840, often called Spanish cloak. Figuratively, "that which covers or conceals, a pretext," from 1520s.
Cloak-and-dagger (adj.) attested from 1848, said to be ultimately translating French de cape et d'épée, suggestive of stealthy violence and intrigue. Compare cloak-and-sword (1806) in reference to melodramatic romantic adventure stories.
Other "cloak and dagger pieces," as Bouterwek tells us the Spaniards call their intriguing comedies, might be tried advantageously in the night, .... ["Levana; or the Doctrine of Education," English translation, London, 1848]
cover with or as with a cloak," "c. 1500, from cloak (n.). Figuratively, "to cover up, hide, conceal" from 1540s. Related: Cloaked; cloaking.