redoubtable

Etymology

The adjective derives from Late Middle English redoutable ("worthy of honour, venerable; frightening, terrible"), borrowed from Anglo-Norman redoutable and Middle French redoutable, redoubtable, from Old French redotable (modern French redoutable), from redoter ("to fear", giving Middle French redoubter, redouter, French redouter) plus -able (a suffix meaning 'deserving of, worthy of'). Redoter itself comes from re- (an intensifying prefix) and doter ("to doubt; to fear"), from Latin dubitō ("to doubt, be uncertain, waver in opinion"), probably ultimately from Proto-Indo-European *dwi- ("apart, asunder; two") and *bʰuH- ("to appear; to be; to become; to grow"), reflecting the idea of being in two minds. By its surface form it also matches redoubt ("to dread") + -able. The noun developed from the adjective.