redoubt n.

late 14c., reducen, "bring back" (to a place or state, a sense now obsolete), also "to diminish" (something), from Old French reducer (14c.), from Latin reducere "lead back, bring back," figuratively "restore, replace," from re- "back" (see re-) + ducere "bring, lead" (from PIE root *deuk- "to lead").

In Middle English largely with positive senses, including "bring back to virtue, restore to God; bring back to health." The specific meaning "bring to an inferior condition" is by 1570s; that of "bring to a lower rank" is by 1640s (military reduce to ranks is from 1802); that of "subdue by force of arms" is from 1610s. The sense of "to lower, diminish, lessen" is from 1787. Related: Reduced; reducing.

late 14c., of persons, "worthy of honor, venerable" (a sense now obsolete); late 15c., "that is to be dreaded or feared, formidable, terrible," also often "valiant," from Old French redoutable (12c.), from redouter "to dread," from re-, intensive prefix, + douter "be afraid of" (see doubt (v.)).

The verb also was in Middle English, redouten, "to fear, dread; stand in awe or apprehension of; honor" (late 14c., from Old French) and was used through 19c., though OED marks it "now rhetorical."