The verb is from Old French redouter, from Latin dubitāre (“doubt”) prefixed with re-. The b was later added back in this word, and the related doubt and redoubtable, to reflect their Latin source.
The noun is unrelated, being via French redoute from Italian ridotta, from Medieval Latin reductus (“refuge”), from Latin reduco (“I withdraw”), and its spelling is taken over from the verb.
redoubt (plural redoubts)
- A small, temporary, military fortification.
- A reinforced refuge; a fort.
- A place of safety or refuge.
redoubt (third-person singular simple present redoubts, present participle redoubting, simple past and past participle redoubted)
- (archaic) To dread.