Meaning

adjective characterized by propriety and dignity and good taste in manners and conduct

adjective according with custom or propriety

originFrom the following: * Latin decōrus (“becoming, fitting, proper, suitable”) + English -ous (suffix adjectives denoting presence of a quality in any degree, typically an abundance). Decōrus is derived from decor (“elegrance, grace; charm beauty”) + -us (suffix forming adjectives); and decor is from decēre, the present active infinitive of decet (“to adorn; to be decent; to be proper or suitable”),…

Etymology from Wiktionary, CC BY-SA 3.0