Etymology
rag (n.1)

"torn or worn scrap of cloth," early 14c., probably from a Scandinavian source (compare Old Norse rögg "shaggy tuft, rough hair," earlier raggw-; Old Danish rag; see rug), or else a back-formation from ragged. It also may represent an unrecorded Old English cognate of Old Norse rögg. In any case, from Proto-Germanic *rawwa-, from PIE root *reue- (2) "to smash, knock down, tear up, uproot" (see rough (adj.)).

Also in Middle English "a hard, rough piece of stone" (late 13c.). As an insulting term for "newspaper, magazine" it dates from 1734; slang for "tampon, sanitary napkin" is attested from 1930s (on the rag "menstruating" is from 1948). Rags "tattered clothing" is from mid-14c.; in the jocular sense of "personal clothing" it is attested by 1855 (singular), American English. Rags-to-riches as a description of a tale of a rise from poverty to wealth is attested by 1896. Rag-picker is from 1860; rag-shop, one selling old clothes, is from 1829.

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rag (v.)

1739, "to scold," a word of unknown origin; perhaps related to Danish dialectal rag "grudge." Compare bullyrag, ballarag "intimidate" (1807). Weakened sense of "annoy, tease, harass roughly" is student slang, by 1808. Related: Ragged; ragging.

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rag (n.2)

"piece of ragtime music," by 1897; see ragtime.

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rag-bag (n.)

"bag in which scraps of clothing are stored," 1820, from rag (n.1) + bag (n.). Figurative sense of "motley collection" is by 1864.

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rag-doll (n.)

child's plaything, doll made entirely of rags or scraps of cloth, 1776 (from 1757 as "a dressed-up woman"), from rag (n.1) + doll (n.). Rag-baby is attested from 1798. Shakespeare has babe of clowts (i.e. "clouts"), 1590s.

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do-rag (n.)

by 1973 (said in DAS to date to 1960s), African-American vernacular, from hairdo + rag (n.1).

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ragtop (n.)

"convertible car with a soft top," 1954, from rag (n.1) + top (n.1).

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raghead (n.)

insulting term for "South Asian or Middle Eastern person," 1910, from rag (n.1) + head (n.); in reference to turbans, etc.

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reggae (n.)
1968, Jamaican English (first in song title "Do the Reggay" by Toots & the Maytals), perhaps [OED, Barnhart] related to rege-rege "a quarrel, protest," literally "ragged clothes," variant of raga-raga, alteration and reduplication of English rag (n.).
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ragtag (n.)
also rag-tag, "ragged people collectively," 1820, from rag (n.) + tag (n.); originally in expression rag-tag and bobtail "the rabble" (tag-rag and bobtail is found in 1650s), with bobtail an old 17c. word for "cur." Tag and rag was "very common in 16-17th c." [OED]
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