mannerly (adj.)

"seemly, modest," late 14c. (a sense now obsolete); "well-mannered, polite, showing good manners," 1520s; from manner (n.) + -ly (1). As an adverb, "in accord with custom; becomingly" (mid-14c.); later "in accord with good manners" (c. 1400). Related: Mannerliness.