the.com/secret passage

means A hidden corridor or doorway built into a structure to allow concealed movement in or out.

from The phrase simply joins 'secret' (from Latin secretus, 'set apart, hidden' — itself from secernere, 'to separate') with 'passage' (from Old French passage, a way through, rooted in Latin passus, 'step' or 'pace'). There's no single secret-passage word to trace — the concept is ancient and practical: castles, temples, and manor houses across many cultures built hidden routes for escape, spying, or smuggling priests and treasure past enemies. The term we use is just English plainly naming the thing: a passage that is secret.