Attested since the 1830s. Probably a shortening or back-formation from Scots tweedling (“a type of twilled cloth”), attested since the 16th century and related to tweedle; the two words are variants of tweeling and tweel, which go back to Middle English twel, twyle (“a type of woven fabric; twill”), whence also English twill. Scottish tradition says it derives directly from tweel when an English merchant misread tweels or tweeled (cloth) in an 1831 letter from a Scottish merchant as Tweed(s) and took it to be a trade-name based on the River Tweed, but the DSL says evidence for this is lacking, and because English merchants must have been familiar with tweel(ed cloth) before the 1830s, it seems unlikely to be based on misunderstanding tweel rather than on the well-attested tweedle. Several of the earliest citations, from 1839, 1841, and 1845 treat it as a new name for a familiar cloth.