ETYM Perh. from Old Fren. de murs (i. e., de bonnes murs of good manners); de of + murs, mours, meurs, mors, French moeurs, from Latin mores (sing. mos) manners, morals (see Moral); or more prob. from Old Fren. meür, French műr mature, ripe (see Mature) in a phrase preceded by de, as de műre conduite of mature conduct.
1. Of sober or serious mien; composed and decorous in bearing; of modest look; staid; grave.
2. Affectedly modest, decorous, or serious; making a show of gravity.