Emily Dickinson Lexicon

DE'CEN-CY, n. [Fr. decence; L. decentia, from decens, deceo, to be fit or becoming; Sp. decencia; It. decenza. The L. deceo coincides in elements with the G. taugen, to be good, or fit for; D. deugen, to be good or virtuous; Sax. dugan, to avail, to be strong, to be worth; duguth, virtue, valor; dohtig, doughty; dohter, daughter; W. tygiaw, to prosper, to befit; to succeed. The Teutonic and Welsh words have for their radical sense, to advance or proceed, to stretch forward. In Welsh also, têg signifies clear, fair, smooth, beautiful; tegu, to make smooth, fair, beautiful, which would seem to be allied to deceo, whence decus, decoro. See Class Dg, No. 18, 25.]

1. That which is fit, suitable or becoming, in words or behavior; propriety of form, in social intercourse, in actions or discourse; proper formality; becoming ceremony. It has a special reference to behavior; as, decency of conduct; decency of worship. But it is used also in reference to speech; as, he discoursed with decency. Those thousand decencies, that daily flow / From all her words and actions. – Milton.
2. Suitableness to character; propriety.
3. Propriety in speech; modesty; opposed to ribaldry, or obscenity. Want of decency is want of sense. – Pope. It may be also used for propriety of speech, opposed to rudeness, or disrespectful language; and for propriety in dress, opposed to raggedness, exposure of nakedness, filthiness, &c.