couth (adj.)

Old English cuðe "known," past participle of cunnan (see can (v.1)), from Proto-Germanic *kunthaz (source also of Old Frisian kuth "known," Old Saxon cuth, Old High German kund, German kund, Gothic kunþs "known"), from PIE root *gno- "to know."

Died out as such 16c. with the emergence of could, but the old word was reborn 1896, with a new sense of "cultured, refined," as a back-formation from uncouth (q.v.). The Old English word forms the first element in the man's proper name Cuthbert, literally "famous-bright."