Webster's Revised Unabridged Dictionary · 1913

Decorum

Decorum , noun

[Latin decōrum, from decōrus. See Decorous.]

Propriety of manner or conduct; grace arising from suitableness of speech and behavior to one's own character, or to the place and occasion; decency of conduct; seemliness; that which is seemly or suitable.
Negligent of the duties and decorums of his station. — Hallam
If your master Would have a queen his beggar, you must tell him, That majesty, to keep decorum, must No less beg than a kingdom. — Shakespeare