carpetbag n.

late 13c.,carpet, carpete, "coarse cloth;" mid-14c., "tablecloth, bedspread;" from Old French carpite "heavy decorated cloth, a carpet" (Modern French carpette), from Medieval Latin or Old Italian carpita "thick woolen cloth," probably from Latin carpere "to card, pluck" (from PIE root *kerp- "to gather, pluck, harvest"). Thus it is so called because it was made from unraveled, shredded, "plucked" fabric. The English word is attested from 15c. in reference to floor coverings, and since 18c. this has been the main sense. The smaller sort is a rug.

Formerly the carpet (usually in a single piece, like the Persian carpet) was also used (as it still is in the East) for covering beds, couches, tables, etc., and in hangings. [Century Dictionary]

From 16c.-19c., by association with luxury, ladies' boudoirs, and drawing rooms, it was used as an adjective, often with a tinge of contempt, in reference to men, as in carpet-knight, 1570s, one who has seen no military service in the field; carpet-monger, 1590s, a lover of ease and pleasure, i.e. one more at home on a carpet.

On the carpet "summoned for reprimand" is by 1900, U.S. colloquial (but compare carpet (v.) "call (someone) to be reprimanded," 1823, British servants' slang). This may have merged with older on the carpet "up for consideration" (1726) literally "on the tablecloth," with the word's older sense, hence "a subject for investigation." To sweep or push something under the carpet in the figurative sense is recorded by 1953.

"small sack," c. 1200, bagge, probably from Old Norse baggi "pack, bundle," or a similar Scandinavian source. OED rejects connection to other Germanic words for "bellows, belly" as without evidence and finds a Celtic origin untenable. In some senses perhaps from Old French bague, which is also from Germanic.

As disparaging slang for "woman" it dates from 1924 in modern use (but various specialized senses of this are much older, and compare baggage). The meaning "person's area of interest or expertise" is by 1964, from African-American vernacular, from jazz sense of "category," probably via notion of putting something in a bag. The meaning "fold of loose skin under the eye" is by 1867. Related: bags.

To be left holding the bag (and presumably nothing else), "cheated, swindled" is attested by 1793. Many figurative senses, such as the verb meaning "to kill game" (1814) and its colloquial extension to "catch, seize, steal" (1818) are from the notion of the game bag (late 15c.) into which the product of the hunt was placed. This also probably explains modern slang in the bag "assured, certain" (1922, American English).

To let the cat out of the bag "reveal the secret" is from 1760. The source is probably the French expression Acheter chat en poche "buy a cat in a bag," which is attested in 18c. French and explained in Bailey's "Universal Etymological English Dictionary" (1736), under the entry for To buy a pig in a poke as "to buy a Thing without looking at it, or enquiring into the Value of it." (Similar expressions are found in Italian and German; and in English, Wycliffe (late 14c.) has To bye a catte in þo sakke is bot litel charge). Thus to let the cat out of the bag would be to inadvertently reveal the hidden truth of a matter one is attempting to pass off as something better or different, which is in line with the earliest uses in English.

Sir Joseph letteth the cat out of the bag, and sheweth principles inimical to the cause of true philosophy, by wishing to make great men Fellows, instead of wise men ["Peter Pindar," "Peter's Prophecy," 1788]

also carpet-bagger, 1868, American English, scornful appellation for Northern whites who set up residence in the South after the fall of the Confederate states seeking private gain or political advancement. The name is based on the image of men arriving with all their worldly goods in a carpetbag. The sense later was extended to any opportunist from out of the area (such as wildcat bankers or territorial officers in the West).

[A]n opprobrious term applied properly to a of adventurers who took advantage of the disorganized condition of political affairs in the earlier years of reconstruction to gain control of the public offices and to use their influence over the negro voters for their own selfish ends. The term was often extended to include any unpopular person of Northern origin living in the South. [Century Dictionary]