late 15c., "well-mannered, courteous, having manners befitting a court," from court (n.) + -ly (1). Compare courteous. Meaning "pertaining to the court" is from late 15c. The elegant, polite, refined courtly love "highly conventionalized medieval chivalric love" (amour courtois) is attested from 1821. Related: Courtliness.

"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.

late 12c., fulthe, "corrupt, sinful," from filth + -y (2). Meaning "physically unclean, dirty, noisome" is from late 14c. Meaning "morally dirty, obscene" is from 1530s.

In early use often hardly more emphatic than the mod. dirty; it is now a violent expression of disgust, seldom employed in polite colloquial speech. [OED]

Related: Filthily; filthiness.

"that may not be or should not be mentioned," 1833, from un- (1) "not" + mentionable (adj.). Humorous use of unmentionables "trousers" is attested by 1806 (see inexpressible); from 1910 as "underwear," both on notion of "articles of dress not to be mentioned in polite circles."

1660s, "suitable, appropriate;" 1670s, "characterized by or notable for decorum, formally polite and proper," from Latin decorus "becoming, seemly, fitting, proper," from decus (genitive decoris) "an ornament," "to decorate, adorn, embellish, beautify," from PIE root *dek- "to take, accept" (on the notion of "to add grace"). Related: Decorously; decorousness.

also pig-tail, 1680s, "tobacco in a twisted roll," from pig (n.1) + tail (n.). So called from resemblance. Meaning "braid of hair hanging down the back of the head" is from 1753, when it was a fashion in polite society; the style was preserved into early 19c. by soldiers and sailors. Since applied variously to other objects or parts thought to resemble this in appearance. Related: Pigtailed.

instrument for examining the chest, 1820, from French stéthoscope, coined 1819 by its inventor, French physician René-Théophile-Hyacinthe Laënnec (1781-1826) from Greek stēthos "chest, breast" + -scope. Greek stēthos is perhaps related to sternon (see sternum); it meant "front of the chest," and was only rarely used of a woman's breasts, but in Modern Greek it became the preferred polite term. Related: Stethoscopic; stethoscopy.

"instinctive knowledge of the right course of action in any circumstance, faculty of knowing just what to do and how to do it," 1815 (Scott), a French phrase in English, literally "to know (how) to do," from savoir "to know" (from Latin sapere; see sapient) + faire (from Latin facere "to make, do;" from PIE root *dhe- "to set, put"). French also has savoir-vivre "knowledge of and ability in the usages of polite society; knowledge of customs in the world," which turns up in English writers, occasionally, in italics.

c. 1300, curteis, "having elegant manners, well-bred, polite, urbane," also "gracious, benevolent," from Old French curteis (Modern French courtois) "having courtly bearing or manners," from curt "court" (see court (n.)) + -eis, from Latin -ensis.

Rare before c. 1500. In feudal society, also denoting a man of good education (hence the name Curtis). Medieval courts were associated with good behavior and also beauty; compare German hübsch "beautiful," from Middle High German hübesch "beautiful," originally "courteous, well-bred," from Old Franconian hofesch, from hof "court." Related: Courteously (mid-14c., kurteis-liche).