haircloth (n.)

Old English hær "hair, a hair," from Proto-Germanic *hēran (source also of Old Saxon, Old Norse, Old High German har, Old Frisian her, Dutch and German haar "hair"), perhaps from PIE *ghers- "to stand out, to bristle, rise to a point" (source also of Lithuanian šerys "bristle;" see horror).

Spelling influenced by Old Norse har and Old English haire "haircloth," from Old French haire, from Frankish *harja or some other Germanic source (see above). Hair-dye is from 1803. To let one's hair down "become familiar" is first recorded 1850. Homeopathic phrase hair of the dog (that bit you), remedy from the same thing that caused the malady, especially a drink on the morning after a debauch, 1540s in English, is in Pliny.

"woven fabric, pliable stuff made of intertexture of threads or fibers," Old English claþ "a cloth, sail, cloth covering, woven or felted material to wrap around one," hence, also, "garment," from Proto-Germanic *kalithaz (source also of Old Frisian klath "cloth," Middle Dutch cleet, Dutch kleed "garment, dress," Middle High German kleit, German Kleid "garment"), which is of obscure origin, perhaps a substratum word.

As an adjective, "made or consisting of cloth," from 1590s. Meaning "distinctive clothing worn by some group" (servants of one house, men of some profession or trade) is from 1590s, hence The cloth "the clerical profession" (1701).